Search by distance facet type

[williamhoos]

Add a facet type to search by distance.

Assume this requires:

• Adding the currently mapped lat/long info to elasticsearch index (locations table in clinwiki used for displaying facilities on the map on the study page) - need to understand how multiple lat/lon values should be stored for a study's facilities
• Adding configurability options to site_view facet choices (what "Field" in index does this point to, what options are provided for how to enter the "search from" location and what is the UI for the facet - just a zipcode, a full address, lat/long from a look up, the "location" pulled from the browser?

[williamhoos]

elastic's geo search: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-geo-distance-query.html

maybe useful article https://codeburst.io/how-to-build-a-yelp-like-search-app-using-react-and-elasticsearch-36a432bf6f92