[aprssig] Telemetry format

[Robert Bruninga]

> The existing format could be condensed to:
> 
> a1122334455d00
> compare to 
> 111,222,333,444,555,bbbbbbbb

Actually, when you put the 36 bytes of the typical 2 hop header
in front of it, plus say 10 sync bytes and 4 bytes of serial
number, the packet length is then actually a comparison between
64 versus 78 which is only a savings of about 18%

But I do agree that we do need an expandable telemetry set.
What about:

T#SSSS,112233445566778899... To the end for any number of 8 bit
hex pairs

T#SSSS;111222333444555666777888999AAABBB... To the end for any
number of up to 12 bit values.

The serial number is human readable.  The comma implies 2 byte 8
bit HEX values.  The Semicolon implies 3 byte 12 bit HEX
values...  Making the serial number be 4 bytes avoids any match
to the existing T#SSS, format.

Using that delimiter as an indicator of the byte count can be
extended to single byte and to 4 or more bytes or BCD or
whathave we...

WB4APR, Bob