Unified JSON web frontend

[phantamanta44]

This PR:

• adds support for options to the JSON web API
• adds a small JS client library for consuming the web API
• refactors the page renderer to embed page data as JSON which can be processed in client code (instead of raw HTML)

It doesn't address the wikidata caching issue yet; my plan is to redesign EvalM in gf-core as a monad transformer so that we can run wordnet in some kind of stateful monad that lets us keep track of pending and completed requests, which will help with both caching and with the previously-discussed bulk request idea

Of course, there is still more frontend stuff necessary to make the GFpedia templates work with the new system