Add missing GSM-prefixes to printf() calls.
Merge branch 'master' of github.com:RuuviTracker/ruuvitracker_fw
Add GPS checksum calculation. Add a production test for MCU<->GPS serial line. Fix compile warnings about static gps structures.
Remove debug message printing.
Merge branch 'master' of https://github.com/thauta/ruuvitracker_fw into gps

Conflicts:
	src/platform/stm32f4/gps.h
Added gps.is_receiving() to report on Lua