Add initialBrakeMode and initialNeutralDeadband to motor protos

[brettle]

For motors with controllerType of "PWM", these would specify the values to use permanently.
For CAN-controlled motors these would specify the values stored in the controller.

The default for initialBrakeMode should be true.
The default for initialNeutralDeadband should be -1, meaning "whatever the factory default is for the specified controllerType".

Note that PWMMotorMediator.java does not currently support deadbanding or coasting, so that would need to implemented (a la CANMotorMediator.java but not dynamic) as part of this issue.