Fixed #15305 -- Made `Count` aggregate and `.values()` play nice together on...

Fixed #15305 -- Made `Count` aggregate and `.values()` play nice together on `GeoQuerySets`.  Thanks, vrehak for the bug report and milosu for initial patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16797 bcc190cf-cafb-0310-a4f2-bffc1f526a37