Reworked the PCSX2 "BIOS" section + few changes

Currently the BIOS section is confusing and misleading:

It recommends to avoid SCPH-10000, yet it is listed in the table.
It may look like all these files are needed, when the core can run with a single BIOS file.
It may look like the files need to be named exactly like in the table.
Doesn't make sense to list "rom1.bin" as it will be useless by itself.
A .nvm file can't have a specific MD5, as it will be modified depending on the BIOS settings (language, date, etc.).

So I changed the entire section, hopefully it will be more clear.

I also changed a few things:

Removed the no longer used folders and "portable.ini" file.
Removed .cue from the supported extensions, PCSX2 doesn't support .cue atm (and I mean even standalone).
Changed "Restart" and "Multi-Mouse" as not supported. Restart crashes the core and other devices than DS2 are not yet supported by the core.
Added "Legacy" infos for the memory cards section.

It is still far from perfect of course but I believe it will make things a bit less confusing for the users...

Previews:

libretro / docs