split setup and enabling of GPS power save mode
enable saving of GPS configuration
GPS locked transmitter frequency

this commit enables the time pulse feature in the uBlox GPS module. a
small hardware modification enables the tracker to be used with the time
pulse as the clock input.
Merge branch 'gps-frequency'

Conflicts:
	gps.c
	main.c

feature additions from both branches were taken into master.
don't lock time pulse to GNSS
diffrent blip speeds (fix / no fix)
compat. NMEA always has 2 chars for sats
add timeout to si4060 reads
return correct sat values
revert changes to use the uBlox TP as clk source

it soon got clear that the timepulse from the uBlox is not suitable as a
reference clock to the Si4060.

it often locks up, hanging the software, etc. a timeout feature for
failed start attempts was added, but is outcommented now, as it only
hides problems. if this should be handled for real, a proper
reset/reinit framework would be needed.