Added 'How do I automatically set a field's value to the user who last edited the object in the admin?' and 'How do I limit admin access so that objects can only be edited by the users who created them?' to the FAQ

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2120 bcc190cf-cafb-0310-a4f2-bffc1f526a37