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- (tet, pyr, hex) can be identified from their number of faces
  and vertices. For these common shapes can use static `test()`
  method instead of the virtual isA() method.

  This is much cheaper for calling on an individual basis since
  it avoids the overhead of constructing an object.

ENH: tetCell edge/reverseEdge (already had tetEdge)

ENH: defaulting for destructors where possible

STYLE: clear() instead of setSize(0) for plain Lists

STYLE: use bool operator instead of valid()/empty() for autoPtr tests

- use dictionary::get<..> instead of lookup in a few more places

- rationalized some layout and comments

- change contiguous from a series of global functions to separate
  templated traits classes:

    - is_contiguous
    - is_contiguous_label
    - is_contiguous_scalar

  The static constexpr 'value' and a constexpr conversion operator
  allow use in template expressions.  The change also makes it much
  easier to define general traits and to inherit from them.

  The is_contiguous_label and is_contiguous_scalar are special traits
  for handling data of homogeneous components of the respective types.

- reduced clutter when iterating over containers

- 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.

Previously the coordinate system functionality was split between
coordinateSystem and coordinateRotation. The coordinateRotation stored
the rotation tensor and handled all tensor transformations.

The functionality has now been revised and consolidated into the
coordinateSystem classes. The sole purpose of coordinateRotation
is now just to provide a selectable mechanism of how to define the
rotation tensor (eg, axis-angle, euler angles, local axes) for user
input, but after providing the appropriate rotation tensor it has
no further influence on the transformations.

--

The coordinateSystem class now contains an origin and a base rotation
tensor directly and various transformation methods.

  - The origin represents the "shift" for a local coordinate system.

  - The base rotation tensor represents the "tilt" or orientation
    of the local coordinate system in general (eg, for mapping
    positions), but may require position-dependent tensors when
    transforming vectors and tensors.

For some coordinate systems (currently the cylindrical coordinate system),
the rotation tensor required for rotating a vector or tensor is
position-dependent.

The new coordinateSystem and its derivates (cartesian, cylindrical,
indirect) now provide a uniform() method to define if the rotation
tensor is position dependent/independent.

The coordinateSystem transform and invTransform methods are now
available in two-parameter forms for obtaining position-dependent
rotation tensors. Eg,

      ... = cs.transform(globalPt, someVector);

In some cases it can be useful to use query uniform() to avoid
storage of redundant values.

      if (cs.uniform())
      {
          vector xx = cs.transform(someVector);
      }
      else
      {
          List<vector> xx = cs.transform(manyPoints, someVector);
      }

Support transform/invTransform for common data types:
   (scalar, vector, sphericalTensor, symmTensor, tensor).

====================
  Breaking Changes
====================

- These changes to coordinate systems and rotations may represent
  a breaking change for existing user coding.

- Relocating the rotation tensor into coordinateSystem itself means
  that the coordinate system 'R()' method now returns the rotation
  directly instead of the coordinateRotation. The method name 'R()'
  was chosen for consistency with other low-level entities (eg,
  quaternion).

  The following changes will be needed in coding:

      Old:  tensor rot = cs.R().R();
      New:  tensor rot = cs.R();

      Old:  cs.R().transform(...);
      New:  cs.transform(...);

  Accessing the runTime selectable coordinateRotation
  has moved to the rotation() method:

      Old:  Info<< "Rotation input: " << cs.R() << nl;
      New:  Info<< "Rotation input: " << cs.rotation() << nl;

- Naming consistency changes may also cause code to break.

      Old:  transformVector()
      New:  transformPrincipal()

  The old method name transformTensor() now simply becomes transform().

====================
  New methods
====================

For operations requiring caching of the coordinate rotations, the
'R()' method can be used with multiple input points:

       tensorField rots(cs.R(somePoints));

   and later

       Foam::transformList(rots, someVectors);

The rotation() method can also be used to change the rotation tensor
via a new coordinateRotation definition (issue #879).

The new methods transformPoint/invTransformPoint provide
transformations with an origin offset using Cartesian for both local
and global points. These can be used to determine the local position
based on the origin/rotation without interpreting it as a r-theta-z
value, for example.

================
  Input format
================

- Streamline dictionary input requirements

  * The default type is cartesian.
  * The default rotation type is the commonly used axes rotation
    specification (with e1/e2/3), which is assumed if the 'rotation'
    sub-dictionary does not exist.

    Example,

    Compact specification:

        coordinateSystem
        {
            origin  (0 0 0);
            e2      (0 1 0);
            e3      (0.5 0 0.866025);
        }

    Full specification (also accepts the longer 'coordinateRotation'
    sub-dictionary name):

        coordinateSystem
        {
            type    cartesian;
            origin  (0 0 0);

            rotation
            {
                type    axes;
                e2      (0 1 0);
                e3      (0.5 0 0.866025);
            }
        }

   This simplifies the input for many cases.

- Additional rotation specification 'none' (an identity rotation):

      coordinateSystem
      {
          origin  (0 0 0);
          rotation { type none; }
      }

- Additional rotation specification 'axisAngle', which is similar
  to the -rotate-angle option for transforming points (issue #660).
  For some cases this can be more intuitive.

  For example,

      rotation
      {
          type    axisAngle;
          axis    (0 1 0);
          angle   30;
      }
  vs.
      rotation
      {
          type    axes;
          e2      (0 1 0);
          e3      (0.5 0 0.866025);
      }

- shorter names (or older longer names) for the coordinate rotation
  specification.

     euler         EulerRotation
     starcd        STARCDRotation
     axes          axesRotation

================
  Coding Style
================
- use Foam::coordSystem namespace for categories of coordinate systems
  (cartesian, cylindrical, indirect). This reduces potential name
  clashes and makes a clearer declaration. Eg,

      coordSystem::cartesian csys_;

  The older names (eg, cartesianCS, etc) remain available via typedefs.

- added coordinateRotations namespace for better organization and
  reduce potential name clashes.

- nBoundaryFaces() is often used and is identical to
  (nFaces() - nInternalFaces()).

- forward the mesh nInternalFaces() and nBoundaryFaces() to
  polyBoundaryMesh as nFaces() and start() respectively,
  for use when operating on a polyBoundaryMesh.

STYLE:

- use identity() function with starting offset when creating boundary maps.

     labelList map
     (
         identity(mesh.nBoundaryFaces(), mesh.nInternalFaces())
     );

  vs.

     labelList map(mesh.nBoundaryFaces());
     forAll(map, i)
     {
         map[i] = mesh.nInternalFaces() + i;
     }

STYLE: use initial hash size 128 instead of 100 in a few 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.

- make the purpose more explicit, and reduces some work for the
  compiler as well.

- The iterator for a HashSet dereferences directly to its key.

- Eg,

      for (const label patchi : patchSet)
      {
          ...
      }
  vs.
      forAllConstIter(labelHashSet, patchSet, iter)
      {
          const label patchi = iter.key();
          ...
      }

- both autoPtr and tmp are defined with an implicit construct from
  nullptr (but with explicit construct from a pointer to null).
  Thus is it safe to use 'nullptr' when returning an empty autoPtr or tmp.

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_();

- relocate some standard functionality to TimePaths to allow a lighter
  means of managing time directories without using the entire Time
  mechanism.

- optional enableLibs for Time construction (default is on)
  and a corresponding argList::noLibs() and "-no-libs" option

STYLE:

- mark Time::outputTime() as deprecated MAY-2016

- use pre-increment for runTime, although there is no difference in
  behaviour or performance.

- this provides a better typesafe means of locating predefined cell
  models than relying on strings. The lookup is now ptr() or ref()
  directly. The lookup functions behave like on-demand singletons when
  loading "etc/cellModels".

  Functionality is now located entirely in cellModel but a forwarding
  version of cellModeller is provided for API (but not ABI) compatibility
  with older existing user code.

STYLE: use constexpr for cellMatcher constants

- this represents a partial revert for commit 6a0a8b99

ENH: add degToRad() multiplier (useful for scalar fields)

- use degToRad() functions throughout instead of scattered local solutions