POST /api/v1/event_searches.

NOTE: This doesn't yet work with the frontend due to an Ember Data
glitch that IMO plays badly with embedded has-many records[1].  We'll
have to find some other representation of embedding data collectors and
study locations in the event search.

Or maybe I should just switch to Ember Data master, make Pancakes use
BasicAdapter, and be done with it.  It's less formal than RESTAdapter,
but it relies on a SIGNIFICANTLY LOWER number of assumptions.

In fact, yeah, I think I'll do that.

[1]: https://github.com/emberjs/data/issues/768