AntennaTracker: convert to new AP_InertialSensor API
Rover: convert to new AP_InertialSensor API
Replay: convert to new AP_InertialSensor API
VARTest: convert to new AP_InertialSensor API
AP_InertialSensor: fixed example build
AP_Common: added MPU9250 product ID
AP_InertialSensor: added product_id support

fill in parameter from first backend
AP_InertialSensor: implement gyro and accel health monitoring

sensor is healthy if it gave a sample on the last update()
AP_InertialSensor: updated comments