- allows custom tuning of compilation parameters

- '-c' option (as per shell), '-Dkey[=value]' option to provide
  preferences via the command-line. For example,

      etc/openfoam -DWM_COMPILER=Clang -int64  ./Allwmake -j -s -l

  These can also be combined with other options. Eg,

      etc/openfoam -DWM_COMPILER=Clang \
          -c 'wmake -show-path-cxx -show-cxxflags'

- relocated from bin/tools/ => etc/ for easier access

- bin/tools/openfoam.in : for autoconfig-style installation

- Auto-detect if the shell script was executed with openfoam and
  interpret accordingly.

  Simple example,

      --------------
      #!/usr/bin/openfoam
      cd "${0%/*}" || exit   # Run -*-sh-*- from this dir

      blockMesh
      simpleFoam
      --------------

   Note it is NOT currently possible to provide any other parameters
   this way. Eg,

      `#!/usr/bin/openfoam -sp` (NOT)

   This will either fail to run, or result in infinite recursion.

- the foamConfigurePaths script is quite simplistic and aggressive in
  what it changes. This was particularly evident when using it to
  change gcc/clang versions.

  Restructured the corresponding compiler settings to define default
  versions (eg, "default_gcc_version") that limits the scope of
  changes performed by foamConfigurePaths and makes it easier to
  understand if changing manually.

- now use debug 2 for scanner and debug 4 for parser.
  Provided better feedback about what is being parsed (debug mode)

- relocate debug application to applications/tools/foamExprParserInfo

- an empty WM_COMPILE_OPTION is treated internally (in make rules)
  like "Opt"

- an empty WM_COMPILER_TYPE is treated like "system" (system compiler)

- locate where the user is less tempted to change it (#1515).
  It really should be considered an invariant environment variable.

STYLE: wmake -help information to stdout, die errors to stderr

- skip processing OSspecific/MSwindows since this can cause duplicate
  doxygen entries

STYLE: adjust formatting in code templates

STYLE: use std::string methods without extra qualifications

- when using VTK from ParaView sources it can better to tag them as
  such, but simultaneously not mask the ParaView with hardware
  rendering.

  The additional ParaView_MESA_DIR variable allows this.
  The balance of library and path setup is unaffected by this.

DOC: update doc/BuildIssues

- no stderr redirect needed:
    * 'command -v'

- no stdout/stderr redirect needed:
    * 'rm -f'

STYLE: consistent spacing after redirects

- this can help if using std algorithms that return a const reference
  such as std::min() does.

- adjust known gcc/clang compiler versions

- call also be used non-interactively for simple 'one-shot' use of
  OpenFOAM utilities or solvers

STYLE: use dash instead of brackets for '- see www.OpenFOAM.com'

- less cluttered in combination with API information

CONFIG: remove adios1 config files

- the use of 'paraview --version' can be fail if the build host
  doesn't have the necessary graphics. For this case, try to obtain
  the ParaView API number from the associated include directory.

- with 1906, OpenFOAM is purely C++ code and the last toolchain bits C
  code have been avoided. Thus relax the wmake C rule for including
  WM_COMPILE_OPTION. This makes it much easier to add different
  compiler options with fewer files.

  For example, for Broadwell-specific options:

      cd wmake/rules/linux64Gcc
      cp c++Opt c++OptBdw

      edit this file and then use WM_COMPILE_OPTION=OptBdw

- ensure that WM_COMPILE_OPTION is always non-empty

- makes the standard config variables more visible

- this cannot be left as a configurable value (on windows), since it
  needs to be enabled even prior to reading the etc/controlDict file,
  in case the OpenFOAM installation path itself contains spaces.

Caveat: The -Wdeprecated-copy produces many, many compiler warnings