Multilingual metadata

Continuing from the discussion in #1027, I can think of the following to-dos:

- [ ] When resolving an `` tag to a person, should we look at the variant(s)?

- [ ] Since (for now) we have gone with splitting variant names into first/last names, we need script-specific printing rules. But (contra what I argued in #1027) within one script there may be different rules.

- [ ] Should the author page also display all paper-level variants? (It already does something like this for papers with an `id`.)

- [ ] Do we want additional structure for multilingual titles and/or abstracts?

- [ ] Add multilingual metadata for older conferences (there are quite a few)?