[1.2.X] Added a hidden toctree pointing at the index file in the docs to...

[1.2.X] Added a hidden toctree pointing at the index file in the docs to silence a sphinx warning. Backport of [14605].

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14606 bcc190cf-cafb-0310-a4f2-bffc1f526a37