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
For segment, circle, beziers, these are the same in all editors and only
need access to the EDA_SHAPE nature, so we can remove the duplication
entirely.
For TABLECELLs, while the cells are polymorphic in that PCB and SCH
cells are both EDA_SHAPEs (via the TEXTBOXes), the parent TABLES
are not polymorphic, and thus the implementation can't be trivially
de-duplicated. Rather than do something with templates, just keep
it simple for now and maybe look at unifying tables later on.