1) Don't set user layer count right after we've
cleared the enabled user layers. (It will
always be 0 by then.)
2) Allow un-enabled layers in some layer
selectors. (Currently this is just the private
layers selector.
3) Reset the appearance panel layers each time a
footprint is loaded. Also, auto-enable any user
layers that the footprint already has.
4) Footprint editor layer visibility is stored in
the view, not in the boars (as is usual).
Fixes https://gitlab.com/kicad/code/kicad/-/issues/20022
Recommendation is to avoid using the year nomenclature as this
information is already encoded in the git repo. Avoids needing to
repeatly update.
Also updates AUTHORS.txt from current repo with contributor names
