- Query the etc/config.sh/compiler for Gcc/Clang versions

- align wmake have_* scripts to support version query as per current
  develop branch

- use config.sh/ fallbacks when the corresponding *_ARCH_PATH is empty
  (eg, BOOST, CGAL, FFTW).
  This aids when building outside of the regular OpenFOAM environment.

- add '[-+.~]' to the recognized qualifiers.
  This allows simple readable names such as

      WM_COMPILER=Clang-vendor

  but also opens the FUTURE (not yet supported) possibility of
  combining in additional information. For example,

      WM_COMPILER=Clang~openmp
      WM_COMPILER=Clang+cuda~openmp

  by using '+' (add) and '~' (subtract) notation similar to what
  spack uses.

CONFIG: support 'override' rules

- if present, compiler-family 'override' rules are included after
  compiler-family 'general' rules have been included. This allows a
  central means for including dynamically generated content to
  override some values.

  Some examples:

  To handle different gcc versions (system compiler):

  wmake/rules/...Gcc/override

  ```
  ifneq (,$(findstring 9, $(WM_COMPILER)))
      cc  := gcc-9
      CC  := g++-9 -std=c++11
  endif
  ```

  To handle different openmp on Darwin (#1656):

  wmake/rules/darwin64Clang/override

  ```
  # Use libomp (not libgomp) unless openmp is disabled
  ifeq (,$(findstring "~openmp", "$(WM_COMPILER)"))
      COMP_OPENMP = -DUSE_OMP -Xpreprocessor -fopenmp
      LINK_OPENMP = -lomp
  else
      include $(GENERAL_RULES)/no-openmp
  endif
  ```

  This treatment arguably fits into wmake/rules/darwin64Clang/general,
  but it serves to illustrate a possible use case.

- requires -Xpreprocessor
- uses 'libomp' (no 'libgomp' link)

TUT: clean up multiphase tutorials

See merge request !347

1) The sign of radiative flux (qr) for modes Power and HeatFlux was
corrected.

2) Relaxation factor implementation was incomplete. Now caching
valueFraction and refValue from  the previous time step.

- use Clang instead of Gcc for Darwin since this is its system
  compiler. The user can force use of Gcc by using Gcc92 etc.

- make etc/cshrc sed check more robust.

- replace tcsh (${%var}) syntax with ("${var}" != "")

[Fixes and ideas from Alexey Matveichev]

CONFIG: do not source the gperftools environment by default

- this is now an used feature, but can be re-enabled by advanced users
  if required.

- add edit of llvm/mesa/vtk paths. Reduce some verbosity

- include Darwin in foamInstallationTest, foamSystemCheck to avoid
  a false negative.

- as a side-effect of recent changes, command-line stripping of .gz
  extensions on input was lost. For example,

      OK:    surfaceTransformPoints file.stl ...
      Fail:  surfaceTransformPoints file.stl.gz ...

- restore the previous behaviour of silently stripping the '.gz'
  extension on input.

ENH: add triSurface::New selector entry point

- for symmetry with MeshedSurface

  Now the thermal baffle can be extrapolated from a patch which is
  coupled to the bottom patch of the solid region.

  The user can set the T bc on the 'top' patch of the solid.

  The new keyword is 'internal' and its default is true. Check new
  tutorial for an example:

  tutorials/heatTransfer/buoyantSimpleFoam/roomWithThickCeiling/

- can aid when creating source-only or binary-only packages

- reads/write shell elements
  Output elements are "bunched" according to type and their set
  without reordering.

- preliminary reading of solids without extraction.
  Handling of *Surface specifications is not implemented

- enhancement and potential breaking change.

  Nastran surface writer previously used the keyword 'scale' for
  field scaling, which was applied uniformly to all output fields.

  Change the meaning of 'scale' to be geometric scaling
  (consistent with reading triSurfaceMesh etc).

  New 'fieldScale' entry is an optional dictionary of scaling
  parameters.

  Example,

      nastran
      {
          scale   1000;     // [m] -> [mm]
          fieldScale
          {
             "p.*"   0.01;  // [Pa] -> [mbar]
          }
      }

- adjustments to internal handling to improve run-time addition of
  other formats (eg, with additional user library)

  For example, to write a binary STL with a '.stl' extension:

    $ surfaceMeshConvert input.obj  -write-format stlb  output.stl

  Or in a sampler,
  to specify the input type without ambiguity:

  surf
  {
      type        meshedSurface;
      surface     sampling.inp;

      fileType    starcd;
      scale       0.001;
      ...
  }

STYLE: regularize naming for input/output scaling

  * -read-scale   (compat: -scaleIn)
  * -write-scale  (compat: -scaleOut)

CONFIG: change edge/surface selection name for STARCD format

- now select as "starcd" instead of "inp" to avoid naming ambiguity
  with abaqus

- eg, for a uniform field and auto range.

- had a PrimitivePatch with SubField, but now use const pointField&.

  There is no derivation path from a pointIOField to SubField<point>,
  so a const reference makes more sense.

- face_type, point_type (similar to STL value_type, etc).
  The naming avoids potential confusion with template parameters.

- rename private typedef from ParentType to MeshReference for more
  consistency with polySurface etc.

- regression introduced by 431c9632

  The triSurface dictionary constructor applies the scaling,
  and thus it can be reported, but not applied in triSurfaceMesh

- refactor common exit/abort code

- support single-parameter output. Eg,

    FatalError("some-executable")
        << "Cannot load something\n"
        << exit(FatalError);

- previously used a Pstream::exit() invoked from the argList
  destructor to handle all MPI shutdown, but this has the unfortunate
  side-effect of using a fixed return value for the program exit.

  Instead use the Pstream::shutdown() method in the destructor and allow
  the normal program exit codes as usual. This means that the
  following code now works as expected.

  ```
  argList args(...);

  if (...)
  {
      InfoErr<< "some error\n";
      return 1;
  }
  ```

- orphaned file: extendedFeatureEdgeMeshI.H

- unused primitiveFaceZone typedef.
  Identical to indirectPrimitivePatch typedef

- conversion, sampling, surfMesh