title: NotificationManager and tags
body: <p>I'm trying to figure out what the tag parameter on some of the NotificationManager's methods actually does as the Google documentation sucks a bit here.</p>
  
  <p>Am I right in thinking that I can set a NOTIFICATION_ID for a certain type of notification, for example a SMS message then having a tag unique.</p>
  
  <p>This means when I launch the app, I could just clear all notifications with that ID?</p>
  
  <p>I'm sorry if this is really basic, but Google should explain this better :(</p>