WIP: Search for Community using elasticsearch

First cuts for search feature for Community
The correct way to implement this is to use a phrase suggester or a term suggester which handles this nicely. We decided not to do that because it involves a UI change or atleast I think it needs one. 

Completion suggesters has a thread/subforum/user reference when it returns but a term/phrase suggesters doesn't. That is why using a phrase suggester at this place would need a UI change to handle phrase suggestions differently!