phase-shift and complimentary PWM support

[AcThPaU]

Current PWMio library can only generate single phase PWM. If multiple PWM output is configured, they all have the same phase.

Phase-Shift PWM is an important feature to drive H bridges, steppers and servos.

All micocontrollers supported by CP can generate precise phase-shift PWM. Some even have complimentary PWM which is required for driving H bridges.