mindset_flop.xml: Lower case on storage media's name (Mindset Corporation Mindset floppy discs).
adam_flop.xml: Keep upper case only on the first letter of the system's name (Coleco Adam diskettes).
next_hdd.xml: Put the manufacturer's name on first place (NeXT hard disk images)
Get rid of a couple of copies of the CC0 text. Add header comment to
CC0 files to remind people editing them what the terms are. Also add
some missing XML headers. The header comments in layouts won't bloat
the binary - they get stripped out before compressing, same as any other
comments.
