docs/sources/monodevelop-reference.source: Add a /monodoc/node
element so that documentation is inserted under the appropriate
"MonoDevelop IDE" node (for current/recent monodoc installs).
svn path=/trunk/monodevelop/; revision=126366
main/docs/sources/monodevelop-extension-guide.source,
main/docs/sources/monodevelop-reference.source, main/Makefile.am:
Add support for generating extension model documentation.
svn path=/trunk/monodevelop/; revision=91410