msg: create uORB topic for sensor selection data

msg/CMakeLists.txt

@@ -90,6 +90,7 @@ set(msg_file_names
 	sensor_baro.msg
 	sensor_combined.msg
 	sensor_correction.msg
+	sensor_selection.msg
 	sensor_gyro.msg
 	sensor_mag.msg
 	sensor_preflight.msg

msg/sensor_selection.msg

@@ -0,0 +1,9 @@
+#
+# Sensor ID's for the voted sensors output on the sensor_combined topic.
+# Will be updated on startup of the sensor module and when sensor selection changes
+#
+
+uint32 accel_device_id		# unique device ID for the selected accelerometers
+uint32 baro_device_id		# unique device ID for the selected barometer
+uint32 gyro_device_id		# unique device ID for the selected rate gyros
+uint32 mag_device_id		# unique device ID for the selected magnetometer