Add system time to sensor data

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

Author: thomassedlmayer

osi_sensordata.proto

@@ -336,4 +336,11 @@ message SensorData
     // Virtual detection area of the sensor
     //
     optional VirtualDetectionArea virtual_detection_area = 28;
+
+    // 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 = 29;
 }