The savedata for each game is stored in /savedata/<ProgramID> for NCCH files. ELF files and 3DSX files use the folder 0 because they have no ID information
Got rid of the code duplication in File and Directory
Files that deal with the host machine's file system now live in DiskFile, similarly for directories and DiskDirectory and archives with DiskArchive.
FS_U: Use the correct error code when a file wasn't found
