New tile system

[aleokdev]

This is the BIGGEST refactor I've done for arpiyi yet -- It started with just a new way to create autotiles, but I started refactoring other stuff as well, and I've basically rewritten half of the internals.

Closes #38, closes #43, closes #39, closes #37, closes #34, closes #35 and basically fixes #36. This is a draft PR.
Features:

1. Easier autotile system creation (Which means support for RPGMaker A3 & A4 textures)
2. Pieced sprites -- This is a big one. Basically, you are able to join different parts of a texture into a single sprite, which means less artwork has to be made (also allows for some cool effects as well)
3. Layers will no longer be constrained to a single tileset -- The entire map system has been redone. Tiles of any tileset can be placed in any layer, even if the tileset contains automatic-placement tiles.
4. Most of the internal rendering stuff has been moved to a single file, which means that (hopefully) arpiyi will be able to be ported over to Vulkan more easily.
   Also features a generic renderer, which:
5. Allows for rendering anything instead of what's defined in renderer.hpp.
6. Allows for rendering stuff from the lua scripting API.
7. Has much cleaner code, specially in the renderer implementations.