Add support for relative encoders

[sahil-kale]

A popular encoder type is a relative encoder - these typically output pulses in QEP form which allow them to offer relative motor positions. These can be helpful in commutation purposes as they can offer improved precision in reporting the rotor angle.

Work that needs to be done

• Add support for a base sensor relativeAngleSensor
• Add an estimator that takes the base sensor and performs relevant filtering and potential velocity/accel compensation (perhaps not required? maybe just add in, should be duplicate outta the hall sensor one)
• Add in API for all rotor sensors that allow calibration (not the rotor sensor) to be reset
• Add flag for the control loop to calibrate itself on startup and then call the above api