Fixed #6266: Added note to docs/modelforms.txt pointing out that they're just...

Fixed #6266: Added note to docs/modelforms.txt pointing out that they're just standard forms and have all the same methods as standard forms


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7305 bcc190cf-cafb-0310-a4f2-bffc1f526a37