[1.0.X] Fixed #10776 -- Added metadata targets for the contrib.admin docs, and...

[1.0.X] Fixed #10776 -- Added metadata targets for the contrib.admin docs, and used one of those targets to clarify the SlugField docs. Thanks to ernop for the suggestion, and timo for the patch.

Merge of r10564 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10570 bcc190cf-cafb-0310-a4f2-bffc1f526a37