Fix terrain summoning

[ScornMandark]

Issue: Terrain summoning right now summons a complex building CustomAsset with multiple layers of size and textures. When trying to save a game and come back to it, the buildings re-randomize. If the Freeze Terrain is used, it clears the scripts from the buildings but the main script issues multiple errors.

Fix: Revamp building summoning and building assets to use individual meshes and textures, and randomly select which to summon, not which state to use.

[ScornMandark]

https://api.tabletopsimulator.com/custom-game-objects/#custom-model

Redo as custom model packages, with obj, materials, and colliders in sub-folders in github