Split schema config to support multiple doctypes

- Split the elasticsearch schema config file down into multiple smaller files and merge them together in Ruby.
- Load schemas for multiple doctypes and merge the doctype schema properties together with some core schema properties.
- Support `DELETE` requests for arbitrary doctypes.

I'm expecting this to have a couple of rounds of feedback before it's deemed mergeable.
Are these supposed to be ellipses? I can't find where they came from originally to check :(