baf

Update for the 8 cell configuration

Correctly implement a shared PWM if you opt for a single PWM controller for both inverting and charging.

Add variable for a shared PWM to the battery but still allow for using seperate PWM devices so that we can drive external devices if we have to.

Set the PWM frequency back to 1kHz, turns out the PWM 5V rail wasn't powerfull enough to drive the opti-isolator, back to driving directly instead

Enable the maintenance charger when one of the cells goes below the critical watermark and add some hysterises to keep it within the deviation. Might need calibration, never got there.