user: set lang separate from home place

[synrg]

Make it possible for the user to ,user set lang to set their language to be different from their home place language so that.

This was requested by @naturefold on iNaturalist Discord:

Is there any way to set it that dronefly doesn't show common names in German when I do ,t for example?

[synrg]

This is now partially implemented as of 15749c5 but it needs more work to consistently apply the language overrides in all cases. It would greatly help if the inconsistencies in the API layer were cleaned up.

Here's a non-exhaustive list of improvements that would help complete this feature:

• a user's settings are applied to every call (i.e. via a client session)
• the Taxon object is cleaned up and made consistent
• any API calls bypassing the creation of a Taxon object are eliminated
• the common name abstraction is moved onto the Taxon object
• rethink whether it makes sense to use the common name in the named place when a user does a from query vs. always showing the user's preferred common name