Last major updates?

Major updates:
* Temperature sensors have actually been frozen in telemetry (since May!) due to a bad bug with handling mutexes (bad Steve!), which is why it looked like the computers/cans weren't warming up
* Solar-target commands are changed back from Float2B to int16 to allow for a wider range of offsets, and we don't need the precision of Float2B
* Assorted improvements to GPS handling
* Fixes with respect to thread and program termination (hopefully no more segmentation faults)
* A utility, `playback`, to play back a telemetry file

Merging immediately