[WIP] Logic for generic tile categories

[GalenEvil]

I still need to test to see if it works as intended. How it works is checks in each drawing section to see if the tile exists, and if not it sets the id string to draw of the generic tile into the next step. Item drawing is messy with a long condition chain, so wondering if I should just make it a single generic item and not check to see what specific kind of item it is.

WIP due to needing to think about how to clean up a few things to make it work better, and setting up a test tileset/json combo to check usability and if there are any noticeable speed hits doing this.

[Abalieno]

As explained here: #4236

But more specifically, at runtime or when you load a different tileset, you probably need to make a full index. So that when tiles are actually used it doesn't need to make any check, it just looks up the pre-made index.

[Coolthulhu]

This PR will probably not become mergeable. Closing.