introduce Storage abstraction interfaces
use Storage i/f to load zip and 7z archives, cdi/cue/gdi/chd media,
cheats and to find custom textures.
Use android file picker to add storage. Request persisted access perms.
jni helper classes.
Issue #813
Use UWP version of FindFirstFileEx
Implement basic access() and stat()
Add home dir to list of drives
Allow external storage folders to be added and scanned for games