Fixed #12975 -- Moved the docs for contrib.admindocs out of the template docs...

Fixed #12975 -- Moved the docs for contrib.admindocs out of the template docs and into their own reference section, and significantly improved the documentation of what admindocs can do. Thanks to jabapyth for the report, and whiteinge for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14484 bcc190cf-cafb-0310-a4f2-bffc1f526a37