- use for-range when iterating
- dictionary access/search methods
- autoPtr for memory management

- also replaced a few instances of readIfPresent with opt<> for
  constant values.

- as part of the cleanup of dictionary access methods (c6520033)
  made the dictionary class single inheritance from IDLList<entry>.

  This eliminates any ambiguities for iterators and allows
  for simple use of range-for looping.

  Eg,
      for (const entry& e : topDict))
      {
          Info<< "entry:" << e.keyword() << " is dict:" << e.isDict() << nl;
      }

   vs

      forAllConstIter(dictionary, topDict, iter))
      {
          Info<< "entry:" << iter().keyword()
              << " is dict:" << iter().isDict() << nl;
      }

- use keyType::option enum to consolidate searching options.
  These enumeration names should be more intuitive to use
  and improve code readability.

    Eg,   lookupEntry(key, keyType::REGEX);
    vs    lookupEntry(key, false, true);

  or

    Eg,   lookupEntry(key, keyType::LITERAL_RECURSIVE);
    vs    lookupEntry(key, true, false);

- new findEntry(), findDict(), findScoped() methods with consolidated
  search options for shorter naming and access names more closely
  aligned with other components. Behave simliarly to the
  methods lookupEntryPtr(), subDictPtr(), lookupScopedEntryPtr(),
  respectively. Default search parameters consistent with lookupEntry().

    Eg, const entry* e = dict.findEntry(key);
    vs  const entry* e = dict.lookupEntryPtr(key, false, true);

- added '*' and '->' dereference operators to dictionary searchers.

- more consistent with dictionary method naming. The get<> or
  getList<> returns a value, doesn't read into a existing location.

- allows single or multiple entries

- avoids compiler ambiguity when virtual methods such as
  IOdictionary::read() exist.

- the method was introduced in 1806, and was thus not yet widely used

- 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)

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_();

- the wordHashSet typedef is always available when HashSet has been
  included.

- use default HashTable key (word) instead of explicitly mentioning it

- this permits direct storage of a list with additional matcher
  capabilities

- provide wordRes::matcher class for similar behaviour as previously

- 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

- direct parsing of -funcs to ITstream.
- use direct lookup when the option is a word/string

- this is a provision for defining execute actions that can be called
  largely independently of the normal time-loop constraints. This can
  be useful to provide hooks for sub-cycling, or to define an action
  that can be triggered manually or on some other event.

- in most cases already checked valid() so don't need additional check
  for setting an existing pointer

There are a few issues:
- error would only throw exceptions if not parallel
- if we change this we also need to make sure the functionObjectList
  construction is synchronised
- bounding box overlap was not returning the correct status so the code
  to avoid the issue of 'badly formed bounding box' was not triggered.

When specifying the averaging data, a new `windowType` option is
available, taking the values:

- none: no windowing
- approximate: past functionality (v1706 and earlier)
- exact: exact moving average - will store and write (for restart) all
  fields in the window

- consolidate word::validated() into word::validate() and also allow
  as short form for string::validate<word>(). Also less confusing than
  having similarly named methods that essentially do the same thing.

- more consistent const access when iterating over strings

- add valid(char) for keyType and wordRe

- error::throwExceptions(bool) returning the previous state makes it
  easier to set and restore states.

- throwing() method to query the current handling (if required).

- the normal error::throwExceptions() and error::dontThrowExceptions()
  also return the previous state, to make it easier to restore later.

- makes the purpose clearer.
  In some places, string::resize() is even simpler.

- use C++11 string::back() in preference to str[str.size()-1]

Original commit message:
------------------------

Parallel IO: New collated file format

When an OpenFOAM simulation runs in parallel, the data for decomposed fields and
mesh(es) has historically been stored in multiple files within separate
directories for each processor.  Processor directories are named 'processorN',
where N is the processor number.

This commit introduces an alternative "collated" file format where the data for
each decomposed field (and mesh) is collated into a single file, which is
written and read on the master processor.  The files are stored in a single
directory named 'processors'.

The new format produces significantly fewer files - one per field, instead of N
per field.  For large parallel cases, this avoids the restriction on the number
of open files imposed by the operating system limits.

The file writing can be threaded allowing the simulation to continue running
while the data is being written to file.  NFS (Network File System) is not
needed when using the the collated format and additionally, there is an option
to run without NFS with the original uncollated approach, known as
"masterUncollated".

The controls for the file handling are in the OptimisationSwitches of
etc/controlDict:

OptimisationSwitches
{
    ...

    //- Parallel IO file handler
    //  uncollated (default), collated or masterUncollated
    fileHandler uncollated;

    //- collated: thread buffer size for queued file writes.
    //  If set to 0 or not sufficient for the file size threading is not used.
    //  Default: 2e9
    maxThreadFileBufferSize 2e9;

    //- masterUncollated: non-blocking buffer size.
    //  If the file exceeds this buffer size scheduled transfer is used.
    //  Default: 2e9
    maxMasterFileBufferSize 2e9;
}

When using the collated file handling, memory is allocated for the data in the
thread.  maxThreadFileBufferSize sets the maximum size of memory in bytes that
is allocated.  If the data exceeds this size, the write does not use threading.

When using the masterUncollated file handling, non-blocking MPI communication
requires a sufficiently large memory buffer on the master node.
maxMasterFileBufferSize sets the maximum size in bytes of the buffer.  If the
data exceeds this size, the system uses scheduled communication.

The installation defaults for the fileHandler choice, maxThreadFileBufferSize
and maxMasterFileBufferSize (set in etc/controlDict) can be over-ridden within
the case controlDict file, like other parameters.  Additionally the fileHandler
can be set by:
- the "-fileHandler" command line argument;
- a FOAM_FILEHANDLER environment variable.

A foamFormatConvert utility allows users to convert files between the collated
and uncollated formats, e.g.
    mpirun -np 2 foamFormatConvert -parallel -fileHandler uncollated

An example case demonstrating the file handling methods is provided in:
$FOAM_TUTORIALS/IO/fileHandling

The work was undertaken by Mattijs Janssens, in collaboration with Henry Weller.

Fixed by setting flag which then gets queried by Time. Fixes #420.

ENH: Function objects - updated logic to determine whether or not to instantiate a time-based function object.  Fixes #439

Now the postProcess utility '-region' option works correctly, e.g. for
the chtMultiRegionSimpleFoam/heatExchanger case

postProcess -region air -func "mag(U)"

calculates 'mag(U)' for all the time steps in region 'air'.

Requires gcc version 4.7 or higher