Prevent the file formatter from writing and the file parser from loading
symbol pin alternates that have an empty name or when the alternate name
is the same as the default pin name. Apparently at some point they were
able to be created and saved.
Do not allow SCH_PIN::SetAlt() to set an alternate name when the name
does not exist in the library symbol pin alternate list. This required
fixing the associated QA test.
When updating or changing schematic symbols from library, reset the pin
alternate to the default when the alternate no longer exists in the
symbol.
Do not populate pin alternates context menu with duplicate default pin.
Clear orphaned pin alternates to the default when saving symbols from
symbol editor.
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
