Core: Add a passthrough backend for the filesystem, exposed as SDMC.
Kernel: Add a File object and a getter for it from an Archive object.
Core: Add a Directory object, with both a stub and a passthrough implementations.
Core: Add a method to obtain a Directory from an Archive.
Kernel: Add a Directory object and a getter for it from an Archive object.
FS: Implement OpenArchive, OpenDirectory, OpenFile and OpenFileDirectly calls.
Kernel: Implement the Close command for Archive, File and Directory.