Organisation filtering on unified search

As a user 
I want to filter the search results by Org
So that I can see content that is created by a specific government organisation

![screenshot](http://f.cl.ly/items/3w2B2X2g3x262r323p2W/Screen%20Shot%202014-04-25%20at%2015.48.11.png)

https://www.pivotaltracker.com/story/show/66950220