Merge branch 'master' of https://github.com/cbeighley/piksi_firmware
Call serial.Serial.close() method when SerialLink is closed
Don't call ser.close in SerialLink.close, instead wait for ListenerThread to close it then exit
Merge remote-tracking branch 'origin/master' into HEAD

Conflicts:
	scripts/serial_link.py
Add message for acquisition result
Put u8 at end of struct to avoid __packed__ alignment issues
Refactor acq result message
Take NAP authentication check out of init and put it after usarts_setup
so we can use printf in it rather than screaming_death.
Merge branch 'master' into hardware_bringup_improvements
NAP callbacks must be registered after sbp_setup
Tracking channel 20ms integration WIP
Add option to erase sectors 1-11 of STM flash when flashing new STM
firmware
Merge remote-tracking branch 'origin/master'
Update file end after write to file log.
Flatten out manage acq state machine.
Removed acq_manage structure, replaced by locals in manage_acq().
Squash acq load into a single blocking call.
Swap acq_start and acq_wait_done for a blocking acq_search.
Flattened acquisition state machine.

This involves a nasty hack with thread priorities to deal
with the interrupt not being cleared until the next write
to the nap acq init register.  This should be changed in the
nap to clear the interrupt when the interrupt register is read.
Rework to use new FFT acquisition core.