public static function installed_allocators() {
        $installed = core_component::get_plugin_list('workshopallocation');
        $forms = array();
        foreach ($installed as $allocation => $allocationpath) {
            if (file_exists($allocationpath . '/lib.php')) {
                $forms[$allocation] = get_string('pluginname', 'workshopallocation_' . $allocation);
            }
        }
        // usability - make sure that manual allocation appears the first
        if (isset($forms['manual'])) {
            $m = array('manual' => $forms['manual']);
            unset($forms['manual']);
            $forms = array_merge($m, $forms);
        }
        return $forms;
    }