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.
-----------------------------------
dragon_cart: Sound Extension, and non-working EPROM Programmer, Speech Synthesis, Ultra Drive
dragon_cass: Hang It!
dragon_flex: Chatplus, Diagnostics, Editor and Assembler, Utilities, etc.
dragon_flop: Various releases from PSE, Dragonfire, N.D.U.G., etc.
dragon_os9: Cash and VAT, DragonPlus OS9 Drivers, Stock Control
-----------------------------------
coco_cart: Added Super LOGO and removed all Dragon cartridges
dragon_cart: Moved all Dragon cartridges from coco_cart
dragon_cass: All known cassette dumps
dragon_flop: All known floppy dumps
dragon_flex: FLEX System and other Compusense FLEX releases
dragon_os9: OS-9, BASIC09, C, Dynacalc, Pascal, RMS, Stylograph
dgnalpha_flop: OS-9, NitrOS9, C, Dynacalc, Pascal, RMS, Stylograph, etc.
