protected function loadPluginManagerConfigs()
    {
        foreach ($this->getXml()->xpath('plugins/pluginmanager[@type != ""]') as $pmConfig) {
            $key = (string)$pmConfig['type'];
            $config = $this->createServiceManagerConfig($pmConfig);

            if ($config) {
                $this->manifest['application_config'][$key] = $config;
            }
        }

        return $this;
    }