Allow the deleting of a Packback Avatar from an account, so users can return to the default avatar.
As a user, I want to be able to delete my avatar from the Edit Avatars page, so I can choose to go back to a placeholder image if I so choose.
As a user, I want to be able to delete my avatar from the Edit Avatars page, so I can choose to go back to a placeholder image if I so choose.