Main Menu + Loading Screen Replacement: Old Background

Replaces the main menu background and the five "unknown" backgrounds with the old background from a further-back version of NMRIH. The loading screen version is horizontally flipped so that the keyboard binding image can be displayed alongside it without covering up part of the image in the process. This does not replace any of the map-specific loading screens that accompany all the official maps. It also does not replace the initial loading screen that shows before the main menu loads when starting the game. I'd like to replace that too, but I don't know if I can or where to find the material file in order to do so. If this mod has any issues, feedback is appreciated and I'll try to fix any screwups I might have made.