Solution for adding new map loading screens & thumbnails without conflicts

[CamoRF]

• Currently new textures have to be added to the interface.vpp_pc file.
• Now that adding new textures has been figured out I think there's a compatibility issue with adding new map loading screens and thumbnails because the asm_pc file would conflict between different map releases.
• Maybe some kind of solution for loading loose files and bypassing the asm_pc requirement would solve this if it's possible.