Manage fullscreen textures (I.E. Intro and endings) automatically

[MoArtis]

Similar to #17, and again to avoid more manual work when generating new packs. Also consider a proper output folder structure. Since these files are not part of ROOM_CUT.bin, Classic Rebirth expect them to be in another folder. No such problem with Dolphin packs (it uses hashes to recognize textures, which is slower though).