Yarn Spinner integration progress

The Yarn Spinner System is now being used for the dialogues.

Basic things like having several chars talking to each other, conversation choices, jumping to different nodes (i.e. dialogue parts) and calling nodes directly works very well.

Integrating the Yarn internal variables with my event system is still work in progress.

I also overhauled parts of the footstep system and the platform jumps so it works a bit smoother now.

Maybe it is about time to create a fresh source snapshot soon.