Core: Replace a sprintf in core_timing with StringFromFormat
Merge pull request #107 from lioncash/sprintf

Core: Replace a sprintf in core_timing with StringFromFormat
Common: Return the number of items read/written in IOFile’s methods instead of a boolean.
Common: Rename the File namespace to FileUtil, to match the filename and prevent collisions.
Core: Add a new File class, obtainable from an Archive, and a stub implementation.
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.