This commit enables cadence-based pedal assist for ebikes using
quadrature-style pedal speed sensors.
There are 2 operation modes:
* PAS only: Motor current is based only on pedal feedback
* ADC + PAS: The code will use both ADC and pedal feedback and use
the strongest command to provide seamless overlap when the user is
pedalling and requests extra torque with the throttle.
Signed-off-by: Marcos Chaparro <mchaparro@powerdesigns.ca>