Fixed `fieldlookup` docs cross-reference directive, and added it to the...

Fixed `fieldlookup` docs cross-reference directive, and added it to the queryset reference.  Refs #12930.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@12808 bcc190cf-cafb-0310-a4f2-bffc1f526a37