Pivotcar and N-Wheeled Car "Location" is not in Center of Bounding Box
Description: The N-Wheeled and Pivotcar's location is not at the center of it's bounding box. This is especially visible when more than 2 cars are used. Scenic however relies on this to determine where the robot is on the map and whether or not it has reached the target. Would it be possible to change this without too much trouble? If not, we could potentially make changes on the Scenic side but passing around the needed information will be slightly trickier.
Steps to reproduce: Run the experiments in incidents/incident_74.json
. Note how in experiments 2 and 4 when there are 3 cars the location is near the back of the robot and it bounces off the target.