`NotificationsDetailListFragment` now listens for note changes.

List will refresh if the currently viewed note was changed. Detail view will pop back to list if the note was removed.

Also added a note changed listener, so that `CommentDetailFragment` can be notified when the note changes and update the comment and moderation buttons.

You can test by viewing a notification in the app, then change it somehow (like add a follower, edit the comment, etc)
Should we check here if activity is null?