- less efficient and less portable than using single-pass processing

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2091

which may be optionally overridden by version-specific rules.

For example the default rules for gcc on GNU/Linux x86_64 are in the
wmake/rules/linux64Gcc directory.  If there is a need to change any of
the rules for a specific version of gcc, e.g. gcc-4.8.4 the directory
wmake/rules/linux64Gcc48 may be created into which any of the language
files may be provided containing the rules to override the defaults.

The Makefiles are now in the makefiles sub-directory

The "-f | -force" option in wmakeLnInclude is now "-u | -update" for
consistency with the other scripts.

The "Usage" entry in the headers is now consistently formatted in all
scripts.

This reverts commit c5bea524.

This reverts commit 2e1e671d.

- main mplib rules located in GENERAL_RULES with specializations
  (if any) under RULES. Modest change in a few options files, but
  cleans up the rules directories.

  previously in options:
      include $(RULES)/mplib$(WM_MPLIB)

  now in options:
      sinclude $(GENERAL_RULES)/mplib$(WM_MPLIB)
      sinclude $(RULES)/mplib$(WM_MPLIB)

  For GNU make it would be permissible to write both in a single line.

- more consistent script names
- remove '-help' option from internal scripts

- simplified the logic
- provide direct link to the respective scripts
- provide help from the respective scripts

- place wmkdep and dirToString executables under
  utilbin/$(WM_ARCH)$(WM_COMPILER).
  This helps somewhat when copying rules about, and might help when creating
  general rules.