Keep path for known contacts

[HenrikBo]

It would be nice to allow keeping a known path when sending dm to a contact.

Current solution
The app tries 5 times to send a dm to a contact and it removes the path on the last retry.

Proposed.
Add a toggle on the contact where you keep last known path instead of sending a flood message and remove the path.

Many user has a home companion and there is no need to remove the path once a good connection is established

[hansimgamr]

This looks like a duplicate of #214, which proposes the same per-contact toggle to keep/avoid flood fallback for direct messages — consolidating discussion there might help.