This was accidentally removed when file operations were removed; for
some reason that was tied to the favorites feature.
Add it back in a simpler form.
This is loosely based on WAIO:
- Load akloader from a prebuilt akloader.nds. Must be extracted from a
given kernel.
- Remaining code based on the R4 variant of romloader.cpp
- Add setting to alternate between nds-bootstrap and given kernel
