title: How to exit the App in Xamarin Forms?
body: <p>My project is built with master-detail navigation.
  There are totally three pages in the list named as Resources, Contacts, and Login.
  Everything works fine in iOS, but when the user presses the Droid/WinPhone devices hardware back button, the app should exit.
  Is there any app-exit mechanism for Xamarin Forms which will work on all the devices.? (I mean native code not platform dependent)
  Thanks in advance.</p>