CONFIG: add additional modules/ directory and Module namespace

- any code placed here should provide Allwmake and Allwclean scripts
  and normally have compilation targets into FOAM_APPBIN, FOAM_LIBBIN

  Since there is no standardize places for sources or applications,
  a simultaneous build of a module's doxygen documentation requires
  a minor bit of manual effort. Add (via symlink) the sources into
  the modules/doc/ directory to have them included in the normal
  OpenFOAM doxygen documentation generation.

  A makelink.example file is provided there as an example.

modules/README.md

@@ -0,0 +1,15 @@
+OpenFOAM Modules
+================
+
+This directory is a location to place additional OpenFOAM components
+or tools and have them built as part of the normal OpenFOAM build
+process. It is assumed that each subdirectory contain an appropriate
+Allwmake file, and that they should in all likelihood also build into
+`$FOAM_APPBIN` and `$FOAM_LIBBIN` instead of
+`$FOAM_USER_APPBIN` and `$FOAM_USER_LIBBIN`.
+
+These additional components may be added as git submodules, by script
+or by hand.
+
+To build the doxygen information for the components, it is also
+necessary to link the directories to the doc/ subdirectory.

modules/doc/Allwclean

@@ -0,0 +1,7 @@
+#!/bin/sh
+# Dummy for "wclean -all"
+# Returns true so it does look like an error
+
+echo "skip wclean for modules doxygen directory"
+
+#------------------------------------------------------------------------------

modules/doc/Allwmake

@@ -0,0 +1,7 @@
+#!/bin/sh
+# Dummy for "wmake -all"
+# Returns true so it does look like an error
+
+echo "skip wmake target for modules doxygen directory"
+
+#------------------------------------------------------------------------------

modules/doc/makelink.example

@@ -0,0 +1,11 @@
+#!/bin/sh
+cd ${0%/*} || exit 1
+
+# Manually create doxygen links for module documentation
+
+for dir in cfmesh/meshLibrary
+do
+    [ -d "../$dir" ] && ln -svf ../$dir ${dir##*/}
+done
+
+#------------------------------------------------------------------------------