Make internal linking's River + Query constructors public

[mitchoyoshitaka]

...and restructure them so that they're slightly more configurable, i.e. making the AJAX endpoint URL and result rendering overrideable.

[mitchoyoshitaka]

Patch v1, refactored so they're in wp.lookup.Query and wp.lookup.River. Also introduces wp.utils, but this should probably be moved out into a separate file in the near future.

[koopersmith]

I like this idea, but would prefer to iterate and tighten the code up before making it publicly available. I'd also like to wait until we properly establish a JS namespace.

Mitcho, can you elaborate on your use cases for the exposed Query and River classes?

[wonderboymusic]

This is a relic from 4 years ago. Mitcho, if your passion is still ignited here, please reopen.