title: Google Cloud Messaging: How to show an icon and group messages
body: <p>I have two questions regarding Google Cloud Messaging:</p>
  
  <p>(My push script is PHP, and my client is Corona SDK.)</p>
  
  <ol>
  <li><p>PUSH ICON: Currently, my push messages are displayed on the screen with an icon that looks like an inverted triangle with an exclamation mark inside. How do I make it show my own icon? (Can I dictate the icon from the server, or must this be done on the client?)</p></li>
  <li><p>GROUPING MESSAGES: Currently, if I send three push messages to the phone, they are shown individually in the push list, whereas in other apps, subsequent push messages all replace the previous one, so they only take up one place in the list. How do I accomplish this? Is this the <code>collapse_key</code> value?</p></li>
  </ol>
  
  <p>Thanks!</p>