Revise the user login code.

* 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

modules/user/models/user.php

@@ -20,6 +20,11 @@
 class User_Model extends ORM {
   protected $has_and_belongs_to_many = array("groups");
 
+  var $validation_rules = array(
+    "name" => "required|length[4,32]",
+    "email" => "valid_email",
+    "password" => "required|length[5,40]");
+
   public function __set($column, $value) {
     switch ($column) {
       case "password":