Automate language configuration.

[eggpi]

Much of our per-language configuration can be queried from the MediaWiki API, Wikidata or MediaWiki tables.

For example, PR #41 has ideas for how to determine the category for hidden categories using the API (or the page_props table), and I've used this Wikidata item to figure out the category for articles lacking citations in the past.

This could be just a one-shot script to be run on Tools Labs (where we have all the database replicas as well) to produce a static configuration for a given language, automating stuff like redirects (see #51).

Alternatively, it could be something that runs dynamically at start-up, so we get fresh configuration each time. I'm not sure that would be necessary though, and in that case it would be nice to avoid MediaWiki table dependencies (which make it harder to develop locally). So I think a one-shot script is the best starting point.