title: From UIManagedDocument to traditional Core Data stack
body: <p>I created a new App using UIManagedDocument. While on my devices everything is fine, I got a lot of bad ratings, because there are problems on other devices :(
  After a lot of reading and testing, I decided to go back to the traditional Core Data stack.
  But what is the best way to do this with an app, that is already in the app store?
  How can I build this update? What should I take care of?</p>
  
  <p>Thanks,
  Stefan</p>