adapt doc directory tree structure

doc/contributors/documentation.rst

@@ -0,0 +1,11 @@
+
+
+Documentation
+=============
+
+This documentation is refreshed upon each push to the central repository.
+
+The module reference documentation is generated from the module sources using
+``#.rst:`` tags (compare for instance
+http://autocmake.readthedocs.org/en/latest/module-reference.html#cc-cmake with
+https://github.com/scisoft/autocmake/blob/master/modules/cc.cmake).