Remove the Funder model, replaced by Organization.

Delete the unused and obsolete migration that Funder created.
Add ability to sort search results by different fields.

This doesn't yet work because of an Elasticsearch bug:
https://github.com/elasticsearch/elasticsearch/issues/6639

But once that bug is fixed, or with a different search engine, it should work.
Add Organization model, start work on Indigo standard data importer.