title: Is there a way to add "hidden" data to a GCM (android push) notification?
body: <p>Is there a way to somehow add some data to the Android push notification by the server side?
  So I can parse the added data in my app and do some actions related to it, like an Id or something like that.</p>
  
  <p>Of course it must be "hidden" so the simple message is not the way I want it.</p>