- makes the intent clearer and avoids the need for additional
  constructor casting. Eg,

      labelList(10, Zero)    vs.  labelList(10, 0)
      scalarField(10, Zero)  vs.  scalarField(10, scalar(0))
      vectorField(10, Zero)  vs.  vectorField(10, vector::zero)

- more dictionary-like methods, enforce keyType::LITERAL for all
  lookups to avoid any spurious keyword matching.

- new readEntry, readIfPresent methods

- The get() method replaces the now deprecate lookup() method.

- Deprecate lookupOrFailsafe()
  Failsafe behaviour is now an optional parameter for lookupOrDefault,
  which makes it easier to tailor behaviour at runtime.

- output of the names is now always flatted without line-breaks.
  Thus,

     os << flatOutput(someEnumNames.names()) << nl;
     os << someEnumNames << nl;

  both generate the same output.

- Constructor now uses C-string (const char*) directly instead of
  Foam::word in its initializer_list.

- Remove special enum + initializer_list constructor form since
  it can create unbounded lookup indices.

- Removd old hasEnum, hasName forms that were provided during initial
  transition from NamedEnum.

- Added static_assert on Enum contents to restrict to enum or
  integral values.  Should not likely be using this class to enumerate
  other things since it internally uses an 'int' for its values.

  Changed volumeType accordingly to enumerate on its type (enum),
  not the class itself.

- avoids some doubled slashes

STYLE: simplify concatenation of processor directory names

- instead of   dict.lookup(name) >> val;
  can use      dict.readEntry(name, val);

  for checking of input token sizes.
  This helps catch certain types of input errors:

  {

      key1 ;                // <- Missing value
      key2 1234             // <- Missing ';' terminator
      key3 val;
  }

STYLE: readIfPresent() instead of 'if found ...' in a few more places.

- Since 'bool' and 'Switch' use the _identical_ input mechanism
  (ie, both accept true/false, on/off, yes/no, none, 1/0), the main
  reason to prefer one or the other is the output.

  The output for Switch is as text (eg, "true"), whereas for bool
  it is label (0 or 1). If the output is required for a dictionary,
  Switch may be appropriate. If the output is not required, or is only
  used for Pstream exchange, bool can be more appropriate.

- improves backward compatibility and more naming consistency.
  Retain setMany(iter1, iter2) to avoid ambiguity with the
  PackedList::set(index, value) method.

- this also provides a better separation of the intent
  (ie, inserting a single value, or inserting multiply values)

- eliminate iterators from PackedList since they were unused, had
  lower performance than direct access and added unneeded complexity.

- eliminate auto-vivify for the PackedList '[] operator.
  The set() method provides any required auto-vivification and
  removing this ability from the '[]' operator allows for a lower
  when accessing the values. Replaced the previous cascade of iterators
  with simpler reference class.

PackedBoolList:

- (temporarily) eliminate logic and addition operators since
  these contained partially unclear semantics.

- the new test() method tests the value of a single bit position and
  returns a bool without any ambiguity caused by the return type
  (like the get() method), nor the const/non-const access (like
  operator[] has). The name corresponds to what std::bitset uses.

- more consistent use of PackedBoolList test(), set(), unset() methods
  for fewer operation and clearer code. Eg,

      if (list.test(index)) ...    |  if (list[index]) ...
      if (!list.test(index)) ...   |  if (list[index] == 0u) ...
      list.set(index);             |  list[index] = 1u;
      list.unset(index);           |  list[index] = 0u;

- deleted the operator=(const labelUList&) and replaced with a setMany()
  method for more clarity about the intended operation and to avoid any
  potential inadvertent behaviour.

- The bitSet class replaces the old PackedBoolList class.
  The redesign provides better block-wise access and reduced method
  calls. This helps both in cases where the bitSet may be relatively
  sparse, and in cases where advantage of contiguous operations can be
  made. This makes it easier to work with a bitSet as top-level object.

  In addition to the previously available count() method to determine
  if a bitSet is being used, now have simpler queries:

    - all()  - true if all bits in the addressable range are empty
    - any()  - true if any bits are set at all.
    - none() - true if no bits are set.

  These are faster than count() and allow early termination.

  The new test() method tests the value of a single bit position and
  returns a bool without any ambiguity caused by the return type
  (like the get() method), nor the const/non-const access (like
  operator[] has). The name corresponds to what std::bitset uses.

  The new find_first(), find_last(), find_next() methods provide a faster
  means of searching for bits that are set.

  This can be especially useful when using a bitSet to control an
  conditional:

  OLD (with macro):

      forAll(selected, celli)
      {
          if (selected[celli])
          {
              sumVol += mesh_.cellVolumes()[celli];
          }
      }

  NEW (with const_iterator):

      for (const label celli : selected)
      {
          sumVol += mesh_.cellVolumes()[celli];
      }

      or manually

      for
      (
          label celli = selected.find_first();
          celli != -1;
          celli = selected.find_next()
      )
      {
          sumVol += mesh_.cellVolumes()[celli];
      }

- When marking up contiguous parts of a bitset, an interval can be
  represented more efficiently as a labelRange of start/size.
  For example,

  OLD:

      if (isA<processorPolyPatch>(pp))
      {
          forAll(pp, i)
          {
              ignoreFaces.set(i);
          }
      }

  NEW:

      if (isA<processorPolyPatch>(pp))
      {
          ignoreFaces.set(pp.range());
      }

Improve alignment of its behaviour with std::unique_ptr

  - element_type typedef
  - release() method - identical to ptr() method
  - get() method to get the pointer without checking and without releasing it.
  - operator*() for dereferencing

Method name changes

  - renamed rawPtr() to get()
  - renamed rawRef() to ref(), removed unused const version.

Removed methods/operators

  - assignment from a raw pointer was deleted (was rarely used).
    Can be convenient, but uncontrolled and potentially unsafe.
    Do allow assignment from a literal nullptr though, since this
    can never leak (and also corresponds to the unique_ptr API).

Additional methods

  - clone() method: forwards to the clone() method of the underlying
    data object with argument forwarding.

  - reset(autoPtr&&) as an alternative to operator=(autoPtr&&)

STYLE: avoid implicit conversion from autoPtr to object type in many places

- existing implementation has the following:

     operator const T&() const { return operator*(); }

  which means that the following code works:

       autoPtr<mapPolyMesh> map = ...;
       updateMesh(*map);    // OK: explicit dereferencing
       updateMesh(map());   // OK: explicit dereferencing
       updateMesh(map);     // OK: implicit dereferencing

  for clarity it may preferable to avoid the implicit dereferencing

- prefer operator* to operator() when deferenced a return value
  so it is clearer that a pointer is involve and not a function call
  etc    Eg,   return *meshPtr_;  vs.  return meshPtr_();

- use succincter method names that more closely resemble dictionary
  and HashTable method names. This improves method name consistency
  between classes and also requires less typing effort:

    args.found(optName)        vs.  args.optionFound(optName)
    args.readIfPresent(..)     vs.  args.optionReadIfPresent(..)
    ...
    args.opt<scalar>(optName)  vs.  args.optionRead<scalar>(optName)
    args.read<scalar>(index)   vs.  args.argRead<scalar>(index)

- the older method names forms have been retained for code compatibility,
  but are now deprecated

- constructor for empty cell/face/point Zones, with contents to be
  transferred in later.

- ZoneMesh::operator(const word&) to return existing zone or a new empty one.

- use surfFaces() to return the templated list of faces.
  This frees up the method 'faces()' to be used as a virtual method,
  which will be needed at a later stage.

This change ensures that these patches are named consistently so that
they can be looked-up as required in e.g. patchMeanVelocityForce

Moved file path handling to regIOobject and made it type specific so
now every object can have its own rules. Examples:
- faceZones are now processor local (and don't search up anymore)
- timeStampMaster is now no longer hardcoded inside IOdictionary
  (e.g. uniformDimensionedFields support it as well)
- the distributedTriSurfaceMesh is properly processor-local; no need
  for fileModificationChecking manipulation.

Avoids the clutter and maintenance effort associated with providing the
function signature string.

Refinement:
-----------
// Optionally avoid patch merging - keeps hexahedral cells
// (to be used with automatic refinement/unrefinement)
//mergePatchFaces off;

// Optional multiple locationsInMesh with corresponding optional cellZone
// (automatically generates faceZones inbetween)
locationsInMesh
(
    ((-0.09 -0.039 -0.049)  bottomAir)  // cellZone bottomAir
    ((-0.09 0.009 -0.049)   topAir)     // cellZone topAir
);

// Optional faceType and patchType specification for these faceZones
faceZoneControls
{
    bottomAir_to_topAir
    {
        faceType baffle;
    }
}

/ Optional checking of 'bleeding' of mesh through a specifying a locations
// outside the mesh
locationsOutsideMesh ((0 0 0)(12.3 101.17 3.98));

// Improved refinement: refine all cells with all (or all but one) sides refined

// Improved refinement: refine all cells with opposing faces with different
// refinement level. These cells can happen on multiply curved surfaces.
// Default on, can be switched off with
//interfaceRefine false;

Snapping
--------
// Optional smoothing of points at refinement interfaces. This will reduce
// the non-orthogonality at refinement interfaces.
//nSmoothInternal $nSmoothPatch;

Layering
--------

// Layers can be added to patches or to any side of a faceZone.
// (Any faceZone internally gets represented as two patches)

// The angle to merge patch faces can be set independently of the
// featureAngle. This is especially useful for large feature angles
// Default is the same as the featureAngle.
//mergePatchFacesAngle 45;

// Optional mesh shrinking type 'displacementMotionSolver'. It uses any
// displacementMotionSolver, e.g. displacementSBRStress
// (default is the medial-axis algorithm, 'displacementMedialAxis')
//meshShrinker displacementMotionSolver;

mattijs authored Oct 14, 2015 and Andrew Heather committed Oct 14, 2015

Refinement:
-----------
// Optionally avoid patch merging - keeps hexahedral cells
// (to be used with automatic refinement/unrefinement)
//mergePatchFaces off;

// Optional multiple locationsInMesh with corresponding optional cellZone
// (automatically generates faceZones inbetween)
locationsInMesh
(
    ((-0.09 -0.039 -0.049)  bottomAir)  // cellZone bottomAir
    ((-0.09 0.009 -0.049)   topAir)     // cellZone topAir
);

// Optional faceType and patchType specification for these faceZones
faceZoneControls
{
    bottomAir_to_topAir
    {
        faceType baffle;
    }
}

/ Optional checking of 'bleeding' of mesh through a specifying a locations
// outside the mesh
locationsOutsideMesh ((0 0 0)(12.3 101.17 3.98));

// Improved refinement: refine all cells with all (or all but one) sides refined

// Improved refinement: refine all cells with opposing faces with different
// refinement level. These cells can happen on multiply curved surfaces.
// Default on, can be switched off with
//interfaceRefine false;

Snapping
--------
// Optional smoothing of points at refinement interfaces. This will reduce
// the non-orthogonality at refinement interfaces.
//nSmoothInternal $nSmoothPatch;

Layering
--------

// Layers can be added to patches or to any side of a faceZone.
// (Any faceZone internally gets represented as two patches)

// The angle to merge patch faces can be set independently of the
// featureAngle. This is especially useful for large feature angles
// Default is the same as the featureAngle.
//mergePatchFacesAngle 45;

// Optional mesh shrinking type 'displacementMotionSolver'. It uses any
// displacementMotionSolver, e.g. displacementSBRStress
// (default is the medial-axis algorithm, 'displacementMedialAxis')
//meshShrinker displacementMotionSolver;

to create single layer extrusions with wedge and empty front and back
patches respectively.