Preserve alternative names of authors from TEI data

[paul-butcher]

Currently, a contributor can only have one name, so we have no way of representing any alternative names of an individual.

The Arabic TEI data is a good example of why this is needed - names are recorded in Arabic and in a Latin alternative (e.g. Avicenna, not necessarily a straight transcription).

For discovery, we should preserve those names.

As an interim measure before the Concepts work is complete enough to have an impact, we could record the multiple names as separate Contributors (?).