title: How to clear old preferences when updating Android app?
body: <p>I have an app on the Google Play market.  For various reasons that I won't bother going into, I have changed the type of some of my preferences.  For example a preference type was an Integer and in the most recent version it is now a String.  I imagine this isn't good practice but unfortunately I had to do it. </p>
  
  <p>My concern is that when someone updates to the new version their app will crash as the preference types have changed.  For this reason I would like to clear the preferences whenever the app is updated (again I realise not ideal!)</p>
  
  <p>Is this possible?</p>