[aprssig] Omni DF support

[scott at opentrac.org]

Is it still only APRSdos and Xastir that support Omni DF'ing?  Also, is
there any way to distinguish between multiple signals, or are all DF plots
assumed to refer to the same target signal?

I'm going to be working with some radios that are frequency-agile and have a
RSSI output.  I want to try implementing an omni DF query that'll cause all
capable stations to QSY briefly to a specified frequency, take a RSSI
measurement, and return to the APRS channel to report their results.
Unfortunately these radios don't cover 121.5, or they'd be good for ELT
DF'ing.

Scott
N1VG