Add system time to sensor data

Signed-off-by: Thomas Sedlmayer <tsedlmayer@pmsfit.de>

Author: thomassedlmayer

osi_sensordata.proto

@@ -313,4 +313,11 @@ message SensorData
     // in cartesian coordinates.
     //
     optional LogicalDetectionData logical_detection_data = 27;
+
+    // The system time of the sensor data, given in UTC (Unix Epoch timestamp).
+    //
+    // The system time can be used to set the corresponding component's internal
+    // time which may not coincide with the simulation time frame.
+    //
+    optional Timestamp system_time = 28;
 }