ENH: distinguish OpenFOAM version for user-coding (fixes #195)

The pre-processor macro 'OPENFOAM_PLUS' is defined with a numerical
value equal to the currently compatible version number.

This can be used judiciously within user coding to help with minor
differences between OpenFOAM versions. For example,

    #ifdef OPENFOAM_PLUS
        #if (OPENFOAM_PLUS >= 1612)
        ...
        #endif
    #endif

or simply

    #if (OPENFOAM_PLUS >= 1612)
    ...
    #endif

See merge request !56

replace system() call with vfork/exec combination (issue #185)

Tested systemCall function object, dynamicCode, but should be rechecked with IB+openmpi
@Prashant

See merge request !55

ENH: OSspecific - softlink handling (fixes #164)

Links are followed in most cases, with some notable exceptions:

- mv, mvBak:
  renames the link, not the underlying file/directory

- rmDir:
  remove the symlink to a directory, does not recurse into the
  underlying directory

See merge request !51

The pre-processor macro 'OPENFOAM_PLUS' is defined with a numerical
value equal to the currently compatible version number.

This can be used judiciously within user coding to help with minor
differences between OpenFOAM versions. For example,

    #ifdef OPENFOAM_PLUS
        #if (OPENFOAM_PLUS >= 1612)
        ...
        #endif
    #endif

or simply

    #if (OPENFOAM_PLUS >= 1612)
    ...
    #endif

Fixes #192

so will be out of date (w.r.t bounding box, subdivisions) when the mesh moves.
Only when all cells stays in all the same boxes can you skip rebuilding it
so this was not deemed worthwhile. Fixes #172

STYLE/ENH: reduce code duplication for coded boundary conditions (issue #184)

- relocate common dictionary output into codedBase class

@Mattijs please test with a few examples as well

See merge request !54

The normal library system() command uses 'fork', which causes
problems on IB+OPENMPI.

STYLE: add Foam:: qualifier to system calls to make them easier to spot.

- remove old VTK_CONVEX_POINT_SET code, since VTK_POLYHEDRON exists
  since several years

ENH: improve robustness of paraFoam script

- only check the relevant plugin types,
  fallback to native reader if needed/possible.

- no engrid development since 2013

- return 0 if not under git, since nothing particular can be said
  about the build number.

- explicitly define which git-dir is to be used.
  This ensure we don't accidentally get some values from some unrelated
  project in the parent directory.

Master update for adjusted config and compile with WM_LABEL_SIZE=64



See merge request !52

- explicitly use List<int> instead List<label> for API compatibility,
  even when 64-bit labels are in use.

- explicitly use List<int> instead List<label> for API compatibility,
  even when 64-bit labels are in use.