[WIP] ElasticSearch implementation

* [x] Create index mapping on model creation
* [x] Index on record creation
* [x] Search view, proxy on E/S
* [x] Search with request body
* [ ] Search with URL parameters
* [ ] Reindex on record update
* [ ] Index individual records on model records PUT
* [ ] Test model definition update
* [ ] Test model definition mapping (shapes, etc.)
* [ ] Test model record mapping (object, etc.)
* [ ] Test spatial query
* [ ] Return specific response code when *elasticsearch* not available/reachable
Note: http://docs.pylonsproject.org/projects/pyramid/en/latest/narr/events.html#creating-your-own-events

(helper would still be relevant)