R1:0bcc76151e6f

Workboards

Summary: Adds Workboards and workpanels. This is a preliminary diff, I'm still working on mobile and tablet and a few missing features (header actions)

Test Plan: FF, Chrome, iOS, iPad, iPhone, IE

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5455