Add a common name language selector

[ezwelty]

I propose that common names default to the interface language selection (as they do now) but that this language be separately configurable by adding a second language dropdown. We would then have two: one for interface language, another for common names. Furthermore, I suggest that it be an ordered multi-select (like we have for location types) so that one can choose a primary language, then subsequence fallback languages.

For example, one might have this configuration:

• interface: [French]
• common names: [French, French, German]