[Lowfer] Use of NMEA strings for GPS 1 pps time tagging

[Lyle Koehler]

It looks like there isn't any way to turn *off* an NMEA sentence on the
Oncore unit without going back into Motorola binary mode and starting over.
I have been reluctant to do that because of the fear of screwing up the unit
so that it will never talk to me again, but may give it a try some day when
I feel brave. In the meantime, I'll continue to check the AFRICAM clock
against the WWV minutes beep whenever I start the program to make sure it
hasn't missed a second :-)

Lyle