Add getTimezone() procedure to the API

jsonrpc.php

@@ -337,6 +337,13 @@ $server->register('updateSubtask', function($id, $task_id, $title = null, $user_
     return $valid && $subTaskModel->update($values);
 });
 
+/**
+ * Application procedures
+ */
+$server->register('getTimezone', function() use($configModel) {
+    return $configModel->get('application_timezone');
+});
+
 /**
  * Parse incoming requests
  */