Compressed file menu

With this pull RGUI is capable of browsing 7zip files.

Designation of bool is_directory was previously done as attr.b. Now there is a new file enum in file_path.h, which encodes the filetype as attr.i. All GUIs were changed to honor this, however only RGUI handles compressed files currently.

Still broken:
Folders inside 7zip files do not work. It's next on my agenda, but it doesn't really fit inside the current menu scheme. My goal is currently to show all files in the 7z archive with subfolder, when opening a 7z archive. However as mentioned, currently only files in the 7zip root can be used.