/**
  * Download exported data
  * 
  * @param void
  * @return null
  */
 function download()
 {
     require_once PROJECT_EXPORTER_MODULE_PATH . '/models/ProjectExporterOutputBuilder.class.php';
     $output_builder = new ProjectExporterOutputBuilder($this->active_project, $this->smarty, null);
     $filename = $output_builder->getOutputArchivePath();
     if (!is_file($filename)) {
         $this->httpError(HTTP_NOT_FOUND);
     }
     // if
     download_file($filename, 'application/zip', basename($filename), true);
 }