Umstellung auf UTC Timestamp

lib/network_messages/track_message.g.dart

@@ -8,7 +8,7 @@ part of 'track_message.dart';
 
 TrackPosition _$TrackPositionFromJson(Map<String, dynamic> json) =>
     TrackPosition()
-      ..time = json['time'] as String
+      ..time = (json['time'] as num).toInt()
       ..lat = (json['lat'] as num).toDouble()
       ..long = (json['long'] as num).toDouble()
       ..acc = (json['acc'] as num).toInt();