- permit SYSTEMMPI user adjustments via
      etc/config.{csh,sh}/mpi-system
  This can be a convenient place for setting up SYSTEMMPI for OpenFOAM
  without adjusting bashrc, prefs.sh ...

- add a USERMPI type. This represents any generic mpi implementation.
  The user is responsible for supplying an appropriate
  wmake/rules/General/mplibUSERMPI file and managing all settings.

  This type of setup can be useful in combination with specific build
  systems (SPACK, EASYBUILD, etc) or module systems for which the MPI
  variant is part of the installed configuration.

- ignore top-level /build and /platforms directories

- use standard *.sh, *.csh endings

editing the respective settings files.

- foamEtcFile is used to find the files, thus follows the standard
  ~OpenFOAM/fileName expansion mechanism.

- make it easier for non-emacs users to generate some of the
  documentation

- only ignore html files in the main directory, not everywhere.
  This is how we lost FoamFooter.html, FoamHeader.html in doc/Doxygen/ in
  the 1.6.x release

- partial revert for
  commit 9557f2cb

- Rename to a corresponding backup file
  If the backup file already exists, attempt with "01" .. "99" suffix.

- git ignore indexed backup files too

- handle ThirdParty-VERSION properly

- handle wmake/utilbin/ location

- should the wmake/rules/* really be packed with a binary distribution?
  I think this is just left over from before.

- in .gitignore, added other common build targets to be ignored.
  Finalized the move of wmkdep etc to wmake/utilbin/

- the $WM_PROJECT_DIR/.build file is automatically updated.
  This file is (and must be) ignored by git.