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

msg/CMakeLists.txt

@@ -152,6 +152,7 @@ set(msg_files
 	sensor_preflight_mag.msg
 	sensor_selection.msg
 	sensors_status_imu.msg
+	sensors_status.msg
 	system_power.msg
 	takeoff_status.msg
 	task_stack_info.msg

msg/sensor_baro.msg

@@ -3,8 +3,10 @@ uint64 timestamp_sample
 
 uint32 device_id          # unique device ID for the sensor that does not change between power cycles
 
+float32 pressure          # static pressure measurement in Pascals
+
+float32 temperature       # temperature in degrees Celsius
+
 uint32 error_count
 
-float32 pressure	# static pressure measurement in millibar
-
-float32 temperature	# static temperature measurement in deg Celsius
+uint8 ORB_QUEUE_LENGTH = 4

msg/sensors_status.msg

@@ -0,0 +1,15 @@
+#
+# Sensor check metrics. This will be zero for a sensor that's primary or unpopulated.
+#
+uint64 timestamp # time since system start (microseconds)
+
+uint32 device_id_primary       # current primary device id for reference
+
+uint32[4] device_ids
+float32[4] inconsistency       # magnitude of difference between sensor instance and mean
+bool[4] healthy                # sensor healthy
+uint8[4] priority
+bool[4] enabled
+bool[4] external
+
+# TOPICS sensors_status sensors_status_baro sensors_status_mag

msg/vehicle_air_data.msg

@@ -10,3 +10,5 @@ float32 baro_temp_celcius		# Temperature in degrees Celsius
 float32 baro_pressure_pa		# Absolute pressure in Pascals
 
 float32 rho				# air density
+
+uint8 calibration_count     # Calibration changed counter. Monotonically increases whenever calibration changes.