powertrain is in the TrackVehicle, don't need it here
fix to getBraking and Throttle functions
single powertrain/driveline for each track chain system
vehicle constructor change for single powertrain/driveline per track chain system
add functions that would be in an abstract version of this class
remove obsolete BuildSystems().
resize supportRoller body vector to the right size
add function to initialize_roller