Skybox example and working in game.
Need to do something cool to take advantage of it like moving the
camera, but it's there and I know roughly how to make one!
* Added `moves` ledger to Board
* This should help with future work like undo, automated tests,
net-play.
* Refactored 2d and 3d displays to use BoardIndex -> Transform
* This means we can have a generic system set the position of Entities
based on moves on the Board.
* Refactored 2d view to have centered board
* (instead of shifting root entity which had poor behavior
characteristics)
Elijah Voigt