add VehiclePanel and VehicleTableModel
(combine CarPanel and LocomotivePanel to VehiclePanel, combine CarTableModel and LocomotiveTableModel to VehicleTableModel, and add "vehicleType" attribute to determine which vehicle library to use)
add VehiclePanel and VehicleTableModel

combine CarPanel and LocomotivePanel to VehiclePanel, combine
CarTableModel and LocomotiveTableModel to VehicleTableModel, and add
"vehicleType" attribute to determine which vehicle library to use