Consider using pyfilesystem2 for FS classes

[ihaveamac]

I think using this for things like SD and NAND would make things easier to combine it with the rest of the modules.

For example SDFilesystem could use this and then SDTitle just needs to be passed an fs object (which could be SDFilesystem or anything else). The main problem here is compatibility, since SDFilesystem already exists and trying to match the fs api may cause conflicts. (This needs to be researched and tested though. Maybe introduce an sdfs module with an "SDFS" class and deprecate the sd module. Handling ID1 here would have to be re-thought.)

For NAND, this would make it easier to use other stuff like SDTitle on stuff in CTRNAND. Doing so is awkward right now because PyCTR itself does not depend on pyfilesystem2 or pyfatfs, so handling titles and stuff inside the NAND has to be done manually (SDTitle and other stuff expect to be given OS filesystem paths, but with one exception for SDFilesystem).

RomFSReader could also benefit from this. The API is kinda awkward compared to any other filesystem classes.

And also accepting pyfilesystem2 fs paths or objects in any class would increase the possible locations to read files and all that.

(A lot of this was written late at night and so could be wrong or written weirdly, but I had to get these ideas written down or I would forget.)