Search System

[euantorano]

@ATofighi already started a search system, but it may be a good idea to extend it a little.

Ideally, the search system should have a concept of an "indexer", used to index content. The default would obviously be the database, but this approach would allow the easy implementation of advanced search systems such as ElasticSearch for Big Boards.

[JN-Jones]

We should also move the logic somewhere else, atm all querying happens in the controller.

[JN-Jones]

TODO: conversations and the memberlist should be searchable too.

[wpillar]

@mybb/developers I would like to suggest pushing this to Alpha 2, any objections?