update page404() to respond with 404 code and other (#567)

Update page404() and pageDatabaseError() to use proper HTTP status codes
Use pageDatabaseError() if UserSession hits a PDOException
Use BaseController instead of AccountController for database errors

Author: frostbitten

userfrosting/controllers/BaseController.php

@@ -35,7 +35,8 @@ public function __construct($app){
      * Request type: GET
      */
     public function page404(){
-        $this->_app->render('errors/404.twig');
+		$twig = $this->_app->view()->getEnvironment();
+		$this->_app->halt(404,$twig->render('errors/404.twig', $twig->getGlobals())); 
     }
 
     /**
@@ -46,7 +47,8 @@ public function page404(){
      * Request type: GET
      */
     public function pageDatabaseError(){
-        $this->_app->render('errors/database.twig');
+		$twig = $this->_app->view()->getEnvironment();
+		$this->_app->halt(503,$twig->render('errors/database.twig', $twig->getGlobals()));
     }
 
     /**

userfrosting/middleware/usersession/UserSession.php

@@ -91,6 +91,8 @@ public function setup(){
             // If we can't connect to the DB, then we can't create an authenticated user.  That's ok if we're in installation mode.
             error_log("Unable to authenticate user because the database is not yet initialized, invalid, or inaccessible.  Falling back to guest user.");
             error_log($e->getTraceAsString());
+            $controller = new BaseController($this->app);
+            return $controller->pageDatabaseError();
         }
     }
 }