sensors: add baro calibration and cleanup

- sensor_baro.msg use SI (pressure in Pascals)
 - update all barometer drivers to publish directly and remove PX4Barometer helper
 - introduce baro cal (offset) mainly as a mechanism to adjust
relative priority
 - commander: add simple baro cal that sets baro offsets to align with
GPS altitude (if available)
 - create new sensors_status.msg to generalize sensor reporting

src/modules/commander/worker_thread.cpp

@@ -35,6 +35,7 @@
 #include "accelerometer_calibration.h"
 #include "airspeed_calibration.h"
 #include "calibration_routines.h"
+#include "baro_calibration.h"
 #include "esc_calibration.h"
 #include "gyro_calibration.h"
 #include "level_calibration.h"
@@ -144,6 +145,10 @@ void WorkerThread::threadEntry()
 		_ret_value = do_mag_calibration_quick(&_mavlink_log_pub, _heading_radians, _latitude, _longitude);
 		break;
 
+	case Request::BaroCalibration:
+		_ret_value = do_baro_calibration(&_mavlink_log_pub);
+		break;
+
 	case Request::ParamLoadDefault:
 		_ret_value = param_load_default();