Provide a “Zero Yaw” feature (for Field-Oriented Drive)

The navX-Micro gyro “yaw” angle will drift over time (approximately 1 degree/minute). While this does not normally impact the robot during a FIRST FTC or FRC match, if using field-oriented drive during extended practice sessions it may be necessary to periodically “zero” the yaw. Drivers should be provided a simple way (e.g., a joystick button) with which to zero the yaw.