Add TileLayout and cave generation

[idbrii]

There are three parts to this PR:

• cleanup
  • Maybe subjective, but the first few commits make the project easier to work with and fix some bugs.
• Add AsTileLayout
  • This is useful for using the maze output in a game.
• Add cave generation
  • Allows you to take the AsTileLayout grid and modify it to create caves from the maze. This part might be out of scope for LuaMaze, but I used it in a game I made recently and wanted to share.