Directional Shading in Minetest (PR #6165)

This is a small showcase of the "Shading" PR by kaadmy, which in my opinion makes the world feel much more alive :D https://github.com/minetest/minetest/pull/6165 Air Hockey Saloon by Chris Zabriskie is licensed under a Attribution License. Permissions beyond the scope of this license may be available at http://chriszabriskie.com/licensing.