Also deprecate SpeedController in favor of motorcontrol.MotorController and
SpeedControllerGroup in favor of motorcontrol.MotorControllerGroup.
The MotorController interface is derived from the SpeedController interface
so that code such as SpeedController x = new VictorSP(1) continues to
compile (just with a warning).
SpeedControllerGroup and MotorControllerGroup are independent classes;
both implement the MotorController interface.
The wpimath APIs use std::array, which doesn't do size checking. Passing
an array with the wrong size can result in uninitialized elements
instead of a compilation error.
This is a breaking change but is worthwhile to avoid hard-to-debug errors.
