Otherwise, when you change the axis numbering type, and don't update
the start offset string, you get an error on dialog save. Instead,
if the number isn't valid, change it to a valid one.
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
Remove the axis numbering code from ARRAY_OPTIONS
and place in a new class, ARRAY_AXIS. This keeps
the logic for the array item numbering separate from
the logic for the array item geometry.
This simplifies the logic in the ARRAY_OPTIONS class, which
no longer has to deal with the numbering of each axis.
