Docs: Config docs + INI parser integration fixes

*  Removed unnecessary NoOverwriteDict class
*  Removed unnecessary RSTDoc subclass
*  Moved generic translater methods back onto DocBase
*  Included & Adapted Sphinx's rst -> text writer
   for documentation module use.  Added textwriter module.
*  Added a doctree -> text method
*  Changed default render (conv) method on SubtestDoc
   to raw (i.e. rst) output
*  Added a text-summary render (conv) method to SubtestDoc
*  Updated Makefile and Unittests

Signed-off-by: Chris Evich <cevich@redhat.com>