The non-NT portion has been moved to wpiutil.
The NT portion has been moved to ntcore (as NTSendable).
SendableBuilder similarly split and moved.
SendableRegistry moved to wpiutil.
In C++, SendableHelper also moved to wpiutil.
This enables use of Sendable from wpimath and also enables
moving several classes from wpilib to wpimath.
A lot of these are breaking changes. frc::Timer was replaced with the
contents of frc2::Timer. The others were in-place argument changes or
removing deprecated non-unit overloads.
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.
