* Remove user registration link and popup from the theme; this
shouldn't be done in a popup. Use ajaxform to simplify the way
that we load the login popup.
* Create form.html.php, this is a template for Forge based forms.
* Move user validation rules into User_Model and let forms
populate the rules into their forms as useful.
* Undo r18688's changes regarding the REST code. We should never
accept a null resource, this breaks the REST abstraction.
* Change login and user controllers to use Forge which lets us delete
login.html.php and user.html.php since those now are generated by
the theme-owned form template
