Better handling of power outages

[Datorsmurf]

Liam should be able to handle power outages and resume function when power comes back.

Some scenarios to handle:

• Don't try to regain contact with charging station chargingpower is lost.
• Don't launch when no signal i present. (Weird edgecase, reaching full battery during power out...)
• if BWF_DETECTION_ALWAYS = true:
  • Stop and wait for lost bwf-signal to return when out mowing.
• if BWF_DETECTION_ALWAYS = false
  • Only accept a limited time without bwf-signal. Then assume power lost and pause. Need to be able to disable this for Liams running completely without bwf