Provide search

This is work for http://aptivate.kanbantool.com/boards/5986-econsensus#tasks-235197

What I've done is to finish off Stephen's work. (The 2nd WIP on the kanban card.) There are some "wants" from the card that aren't covered by this (boosting of terms within title, filtering by organization); if these are important I suggest creating a new card to carry on with this epic.

There aren't any tests for search, as this complicate the running of the test suite (as elasticsearch would have to be running). Given that it's haystack and elasticsearch that are doing all the heavy lifting, I'm not too worried about this. By default Econsensus is configured with search disabled.