Have repeaters try again if no echo heard

[mikecarper]

DMs and traces where the repeater should hear an echo from the next repeater in the chain; if that fails then have the repeater try sending the same packet again only 1 more time.

Also in the example of a car repeater or rooftop repeater; if the repeater is the first hop of a message and it didn't hear an echo have the repeater try up to 2 more times. The reason to try twice here is it can be a bit of a frustrating experience if you send out a message only for it to travel as far as you can throw a rock; but the companion says all is good.

both of these should be configurable; I'd have both enabled but they could be turned off for the more busy locations.