Add ‘medium’ mode

Actually promoted ‘low’ to medium and added a new ‘low’.
Blink green LED to indicate charge state
Print charge state in debug output
Turn to low, not off if overheating and blink to warn first
Probably don’t need to check temp if off
Increase ‘knob’ sensitivity
Copy fix from factory firmware

Fixed an issue where, in rare circumstances, the button can become
unresponsive due to PD2 floating.