Fixes#2057
• On app launch, the app checks if notification permissions are granted and registers with APNS if that is the case. It will not request permissions as part of the app launch.
• When a user requests to be notified of new articles, the authorizationStatus is checked:
- if `notDetermined` or `provisional`, an authorization request is made, and if successful, the Notify of New Articles status is updated (otherwise it is reverted)
- if `denied`, an alert is thrown asking the user to enable in settings (and the change to notify of new articles is reverted)
- if `authorized` the update is made.
`WebFeedInspectorViewController` also monitors for the app entering the foreground so that it can get the latest notification auth settings.
