Support JSON search results

This is the "simplest thing that could possibly work" approach.

Actually, the *simplest* thing that could possibly work would be a new route that simply does some validation/filtering of input and pipes the request/response with the elasticsearch API back to the client. This would be nice because any elasticsearch-based tools/modules would "just work". However, the current `model` abstraction doesn't seem very amenable to that sort of thing, and there is the "exact-name match must be first" logic to contend with as well.