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/controllers/logout.php

@@ -24,6 +24,8 @@ class Logout_Controller extends Controller {
     } catch (Exception $e) {
       Kohana::log("error", $e);
     }
-    print json_encode(array("logout" => true));
+    if ($this->input->get("continue")) {
+      url::redirect($this->input->get("continue"));
+    }
   }
 }