/**
  * Find a PHP class and instanciate it to replace the empty AJXP_Plugin
  *
  * @param AJXP_Plugin $plugin
  * @return AJXP_Plugin
  */
 private function instanciatePluginClass($plugin)
 {
     $definition = $plugin->getClassFile();
     if (!$definition) {
         return $plugin;
     }
     $filename = AJXP_INSTALL_PATH . "/" . $definition["filename"];
     $className = $definition["classname"];
     if (is_file($filename)) {
         /**
          * @var AJXP_Plugin $newPlugin
          */
         require_once $filename;
         $newPlugin = new $className($plugin->getId(), $plugin->getBaseDir());
         $newPlugin->loadManifest();
         $this->required_files[$filename] = $filename;
         return $newPlugin;
     } else {
         return $plugin;
     }
 }