Active low shoot through fix
Most importantly this release fixes shoot through (all IGBTs on) on the second startup when in active low mode.
Other changes:
- Improved switch between regen and accel by introducing a second PI controller
- Fixed Blue Pill break input - again
- Changed PWM frequency handling - always same controller frequency and 3 possible PWM frequencies - 4.4, 8.8, 17.6kHz
The last change means that I removed 1.1 and 2.2kHz, I hope nobody used it.