Move unfollow protocol to worker task

- Add uid parameter to unfollow hook
- Rework and unify Contact::unfollow, Contact::removeSharer and Contact::terminateFriendship
- Add missing twitterUser property to Twitter\Friendships\Destroy module

src/Worker/Notifier.php

@@ -673,7 +673,7 @@ class Notifier
 		}
 
 		while($contact = DBA::fetch($contacts_stmt)) {
-			Protocol::terminateFriendship($owner, $contact, true);
+			Contact::terminateFriendship($contact);
 		}
 		DBA::close($contacts_stmt);