title: Distinguish between UIRemoteNotificationTypeNone scenarios -- not yet prompted vs. user disabled in Settings
body: <p>We can check if push notifications are enabled with <code>[[UIApplication sharedApplication] enabledRemoteNotificationTypes]</code>, which returns <code>UIRemoteNotificationTypeNone</code> if they aren't enabled.</p>
  
  <p>However, this doesn't distinguish between the disparate cases where the user has yet to be prompted for push notifications, they've been prompted and denied, or they've gone into Settings and turned off notifications.</p>
  
  <p>Is there a way to determine which?  I use a <a href="https://medium.com/on-startups/96fa4eb54f2c" rel="nofollow">pre-prompt</a> before the official permissions dialog, so I need to distinguish between these cases.  Tracking with NSUserDefaults won't work because a user could download the app, turn off push permissions in Settings, then re-install the app.  This clears saved NSUserDefaults but unfortunately doesn't clear their push permissions in Settings, which leads me to pre-prompt the user again even though it's not possible to show the official dialog again.</p>