- supports copy append and move append

- already had remove() by iterator, but not by key.
  As per erase() which already worked by iterator or by key.

- as per 018124e3

Changed into warning since e.g. tutorials/combustion/fireFoam/LES/compartmentFire
uses columns of 1D stacks so they've got empty but are still 3D.

- simplifies usage.
  Support syncPar check on names() to detect inconsistencies.

- simplify readFields, ReadFields and other routines by using these
  new methods.

- what was previously termed 'setLargeCellSubset()' is now simply
  'setCellSubset()' and supports memory efficient interfaces.

  The new parameter ordering avoids ambiguities caused by default
  parameters.

  Old parameter order:

      setLargeCellSubset
      (
          const labelList& region,
          const label currentRegion,
          const label patchID = -1,
          const bool syncCouples = true
      );

  New parameter order:

      setCellSubset
      (
          const label regioni,
          const labelUList& regions,
          const label patchID = -1,
          const bool syncCouples = true
      );

   And without ambiguity:

      setCellSubset
      (
          const labelUList& selectedCells,
          const label patchID = -1,
          const bool syncCouples = true
      );

- support bitSet directly for specifying the selectedCells for
  memory efficiency and ease of use.

- Additional constructors to perform setCellSubset() immediately,
  which simplifies coding.

  For example,

      meshParts.set
      (
          zonei,
          new fvMeshSubset(mesh, selectedCells)
      );

  Or even

      return autoPtr<fvMeshSubset>::New(mesh, selectedCells);

- BitSetOps::create(len, locations, on) that generates a bitSet with
  the specified length. The optional 'on' bool can be used to flip the
  logic.

- enclosed with a #ifdef Foam_argList_1712 .. #endif pair
  (defined by default).
  In a later release, this can be disabled by default.

ENH: add input length check for -hostRoots option

- unused, does not run in parallel

- avoid enclosing namespace in fvMeshSubset

- gets the pointer within the list.

- improve alignment of various phasePairKey implementations

- get<label>, get<scalar> instead of readLabel, readScalar, etc.

- this eliminates a degree of ambiguity when resolving a read() method
  in inherited classes.

- ignore implicit-fallthrough for ragel generated code.

- add -Wno-deprecated-declarations for c++LESSWARN.
  These principally associated with older CGAL versions and their use
  of particular mpfr routines.

- simplifies conversion of RPM to radians/sec for const variables

- improve doxygen for lumpedPointMotion

- ref issue #762

STYLE: consistency in file vs files for pointNoise and surfaceNoise

- use "files" when available, fallback to "file" otherwise.

Some special adjustments are undertaken for distance = 0.

- With the isoSurfaceCell algorithm is used, additional checks for open
  surfaces edges are used to limit the extend of resulting distance
  surface. The resulting surface elements will not, however, contain
  partial cell coverage.

- Always treated as signed (ignoring the input value), since it is
  nearly impossible to generate any surface otherwise.

- missing indexing caused the real radius to be largely ignored
  when useRealRadius = true

- the original intention was to avoid vtp output when the clouds are
  empty anyhow. However, it is useful for post-processing to have
  clouds with zero parcels (eg, before the start of injection).

  Pruning of empty clouds is now an option in the vtkCloud dictionary
  controls, with the default being false (no pruning). This represents
  a non-breaking change in behaviour since it generates more output
  than previously.

  Example,
  {
      type    vtkCloud;
      //- Suppress writing of empty clouds (default: false)
      prune   true;
  }