fix: imaxB6 UART connection problems, increased Vb1 Vb2 accuracy
calibration required
add: enable "expert" calibration menu
Merge https://github.com/stawel/cheali-charger

Conflicts:
	src/hardware/Turnigy-Accucel-6-50W-5A/cheali-charger-Turnigy-Accucel-6-50W-5A.size
	src/hardware/imaxB6-clone/cheali-charger-imaxB6-clone.size
	src/hardware/imaxB6-original/cheali-charger-imaxB6-original.size