[aprssig] New OT1+ SMT features

['Scott Miller']

I've just added a couple of frequently-requested features to the firwmare
for the OT1+ SMT.  First, you can have it send arbitrary text strings by
starting a line with !.  It'll send everything from the ! to the next
carriage return, up to about 110 bytes.  It still enforces the quiet time
setting (it'll hold off if the channel is busy), and uses the configured
TXD, baud rate (300/1200), path, and so on.  The ! isn't transmitted, so you
can format the payload however you want.

Second, if you start the line with @ it'll send the text as CW.  Currently
the rate is hard-coded at something like 15 wpm faster than I can copy,
which means it's probably about 20 wpm.  One dit time is 1/20 second, if
someone wants to figure it out.

These features are mostly geared toward people wanting to run a Basic Stamp
or some other controller in conjunction with the OT1+ board to do additional
telemetry.  You could also use it for barcode applications too, I suppose -
maybe I'll add an optional terminating character so you don't have to
program the barcode reader to send a CR/LF.

73,

Scott
N1VG