First release, working POC

This POC demonstrates a way of simulating heat transfer in a tiled environment. Start in the editor (will take about 30s to 1m), then switch to scene view, and select the "Environment" object in the scene hierarchy, and then click the "Test" button in simulator editor. One tile is set hot enough to make every other tile eventually 100c, after quite a bit of time. Tiles that are walled off by rocks are not affected.