Set body classes via Quicksand config
Summary: Sends and stores additional body classes at the page level. Removes old ones, sets new ones.
Test Plan: home -> application search -> colored workboard -> config -> home with persistent chat open and minimized.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16646