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

Reference manual states these must be set to zero if this case is true.

Broken from the same reason SADD16 was.

The lo part of the result should only be constructed from the lo halfwords of rm and rn.
The hi part of the result should only be constructed from the hi halfwords of rm and rn.

The lo and hi parts of the result were being constructed as a result of hi and lo halfword intermixing from the rm and rn regs. However the lo part of the result should be constructed only from the lo halfwords of rm and rn, and the hi part of the result should only be constructed from the hi halfwords of rm and rn.

Wrong values were being multiplied together.

The only difference between these ops is one adds and one subtracts. Everything is literally the same.

- Refactor FS::Archive internals to make Archive creation and lifetime
  management clearer.
- Remove the "Archive as a File" hack.
- Implement 64-bit Archive handles.

I couldn't find any information about this service...

Apparently nothing at all is known about this service...

This is a first step at fixing the conceptual insanity that is our
handling of service and IPC calls. For now, interfaces still directly
derived from Session because we don't have the infrastructure to do it
properly. (That is, Processes and scheduling them.)

Rotation bits are 10 and 11, not 9 and 10.

Fixes #277

Same semantics, idea by @yuriks