Textures were not loaded properly from PK3/PK7 archives.
Visual mode: restored ability to remove textures using Delete action.
Visual mode: fixed several bugs in Cut/Copy/Paste things actions.
Visual mode: vavoom style 3d floors were not displayed properly.
Visual mode, 3d floors: added support for "RestrictLighting" (2) flag.
Visual mode, 3d floors: inner sides of 3d floors with "swimmable"/"render inside" flags used incorrect brightness value.