-url_exists: verify that an avatar url exists
-avatar_choice_url:return url for a specific avatar
- avatar_url (bug fix) make sure the url exists and create the avatar if
it does not.  This prevents the display of a non primary avatar when
specifying the size in the avatar template tag.
-avatar_url (bug fix) user's  gravatar is now retrieved weather gravitar
default is specified or not.
-allow custom messages
-admin now shows the correct image for avatar
-added settings for custom messages