Further Enhancements to Advanced Coupling

Adds features to animate the couplings as follows:

i) Knuckle couplers will move backwards and forwards with train slack movement and rotate as cars go around curves

ii) Air hoses will move as train slack changes.

Animated coupler features will need to be applied on both player and AI trains, so that all trains are displaying couplers.

The main changes will be in the MSTSWagonViewer class with relevant calculations made mainly in the TrainCar class.

This may be a series of PRs as a number of additional coupler types may need to be considered.

Further discussion and test models are referenced here -

Discussion: http://www.elvastower.com/forums/index.php?/topic/32975-advanced-coupler/