Update admin pages to use PRG pattern

source/webui/pages/admin/site.php

@@ -3,6 +3,7 @@
 $main = StatusBoard_Main::instance();
 $request = $main->request();
 $auth = $main->auth();
+$session = $main->session();
 
 if ( ! $auth->isAuthenticated() || ! $auth->hasPermission(StatusBoard_Permission::PERM_UpdateStatusBoards)) {
     throw new StatusBoard_Exception_NotAuthorised();
@@ -80,6 +81,9 @@ if ($request->exists('do')) {
         }
         
     }
+
+    $session->set('messages', $messages);
+    StatusBoard_Page::redirect("admin/site/service/{$service->id}/id/{$site->id}/");
 }