[aprssig] Beacon rate feedback

[Joseph M. Durnal]

I've often thought that this would be a good idea, but I figure if
everyone was doing it that it could cause trouble, especially with 30
second beacons!

I think a nice hybrid would be ideal.  Something like the proportional
pathing like the TM-D710, but won't fall back to the direct packets if
it hasn't heard the digipeated packets.

Most digis (at least around here) won't repeat a packet that it just
repeated, it seems pretty safe.

73 de Joseph Durnal NE3R