Did some refactoring to remove the ability to start a thread and sleep from core's public API.
Finished rename of TileClass and Tile.
Finished cleaning up models directory.
Cleaned up main core header.
Updated Tiles to the new Tile spec and added some error checking to core for some errors that I ran across while making the Tile changes.
Did a lot of cleanup and started towards allowing startup to load the world from the path.