Better flow for deleting a relationship

Currently _(as discussed in #9)_ we loose the display of a relationship name in consentos when a relationship is deleted. @marcchataigner brought up a better way for handling this:

> Alice cannot delete the relation without the consento of Bob. This would create a situation where Bob is notified and can find another lockee to replace Alice.

We need several things for this to become reality:

1. A new consento that is shown at alice's device that bob is asking for the deletion of a relationship.
- The consento has a display that shows how many vaults (locked with name and unlocked without name) bob is currently a lockee to.
- Only once bob is no lockee to any vault anymore it is possible for Alice to confirm the deletion.
2. A display at the bob's device that shows that alice received the deletion request and it is pending.
3. A means for bob to cancel the deletion request.