Implement some of savedata GETSIZE and DELETEDATA

Attempt to improve #579.  It should at worst log more/better errors now.  My copy gets farther before showing an error anyway.

Most of this was based largely off of stuff in JPCSP.

I got some tests showing timing issues (e.g. `sceUtilitySavedataGetStatus()` should return the same status for X cycles or so), but when I fix them things go bad, so it will need more work.  Delaying `sceUtilitySavedataUpdate()` seemed safe, though, and may fix some situations.

-[Unknown]