[aprssig] ISONLY

[Bill V WA7NWP]

We have RFONLY and NOGATE pseudo path entries to keep packets out of
the APRS-IS.   Why not also have something like "ISONLY" for folks
that only care about being seen on the web services.  As more smart
digipeaters are coming on line that would allow tuning the appropriate
action at a digi.   A digi/IGate combo would know to not digi the
packet at all as it was already Igated locally.  A digi that 'knows'
it has multiple IGates in its coverage area could mark all additional
hops used before resending the packet.

This could potentially reduce lots of extraneous packets on RF.

73
Bill - WA7NWP