implementing multiple modes for operation

implement operationModes:
- local: With local database
- synapse: use register-API of synapse

mail_templates.php

@@ -24,6 +24,7 @@ if (!file_exists($lang_file)) {
     error_log("Mail templates for '" . $lang . "' not found. Fallback to 'de-de'");
     $lang = "de-de";
 }
+$lang_file = dirname(__FILE__) . "/lang/mail." . $lang . ".php";
 require_once($lang_file);
 unset($lang_file);
 ?>