MaVehicles library v0.6.0

• API changes:
  • specify a PhysicsSpace in the World.attach() method
  • changed the semantics of a vehicle's "accelerate" control signal, which now ranges from 0 to 1 instead of -1 to +1
  • made the engine sound an Engine property (instead of a Vehicle one)
  • replaced Sound.addOgg() with addAssetPath() and publicized it
  • deleted public method Vehicle.getRotation()
  • moved the TireGraph class out of the MaVehicles library
• bugfix: engine sounds don't move with the Vehicle
• Publish to MavenCentral instead of JCenter
• new features:
  • SteeringWheelState (split off from the DriverHud class of MavDemo1)
  • an alternative Vehicle.setChassis() that doesn't require assets
  • HasNode and VehicleSteering interfaces
  • Sound.isPositional() and Sound.setPositional() methods
  • assign a name to each AudioNode
  • assign application data to each PhysicsCollisionObject