Explain implicit subscription path like for direct subscriptions

Direct bug subscriptions show the person who added them in a tooltip. They are easy to fix.

Implicit subscriptions don't give any way to determine the reason for their existence. This makes them very difficult to fix. They should have a tooltip saying something like "Subscribed to Malone 2.1.10" or "Assigned to this bug". For bonus points, include an edit button next to the structural subscriptions. Maybe this will even help people to unsubscribe themselves when they manage to subscribe themselves to Ubuntu while looking for ShipIt.