Back-end work for Flow board search.

We need to split off pieces of the CirrusSearch maintenance script, and adapt them to work with Flow data. This will set up the proper config to use Flow data in Elasticsearch.

We need the analyzer for language support, and for highlighting pieces of text. We also need a way to handle when Elasticsearch needs another server.

This will involve some review and support from Chad and Nik.

Split out from https://trello.com/c/5bcxlvcr

Trello card: lYe1ZhNl