Add add a method to read player vehicle movement controls

There are 3 properties in nms.EntityLiving that represent the player's WASD and spacebar state while the player is riding a mount.

This would be very useful for custom vehicle plugins if exposed to the API.

I would propose exposing this as a single Vector, which would be the combination of forward and strafe directions in X/Z and add 1 to Y if spacebar is pressed. This Vector would be relative to the player's look direction, and so not in terms of world coordinates.

I am curious to know what others would think about this, if such a PR would have a possibility of being accepted.