FMod - Persistent mini-palettes

For quite a while now, Abiathar has had mini-palettes, user-decidable arrangements of 9 (10 if you count the ephemeral "previously selected tile" one) tiles for each plane. These are useful if you have a few tiles that are moderately tricky to find - common enough to want to have on hand but not easy to pick out of the tileset or current level. They weren't persisted across Abiathar runs, though, so you had to manually get your tiles arranged again if you restarted. That's pretty unfortunate, so today I made them be persisted in project files. As a side effect of that, they are no longer preserved across opens of different project files, which I think is a good thing because the tile IDs could mean something entirely different in different projects.