Random notes
-Capacitors around the crystal need to be substituted for appropriate values. Most likely 27pF or so.
-Digitpeater callsigns need to be configurable. Weather balloons should be able to be configured for 0 hops, for instance. WIDE-1, WIDE-2 defaults are not sufficient for all cases.
-ax25_recving() should have an int that's 0 or 1, so we can tell when an incoming transmission is over, not just when it starts.
-Report weather from BME280 over APRS + battery percentage
-2 time thresholds: one when moving below a certain speed, and one when above