[aprssig] Tactical call signs

[John Habbinga]

The control operator of the station originating a message is primarily 
accountable for any violation of the rules in this part contained in the 
message.

Digipeated traffic is not 3rd party traffic.  The operator of the 
digipeater, or the I-gate, is not responsible for the content of the 
traffic.  The operator of the digipeater is only responsible for making an 
effort to prevent illegal traffic.

> If it's digipeated then it's 3rd party traffic and the digipeater is
> responsible for IDing itself.  Same goes for an I-Gate.