Remove sidenav from Workboards

Summary: Visually, I think these are much cleaner (with colors), and provide more workspace. I also don't really use the sidenav here and if I did, it would be to go back to the project homepage. I think this is overall better. If navigation page to project home is difficult or hard to find, we can maybe make a better header / crumbs bar to reduce that.

Test Plan: New project -> basic new board. Existing project -> color board. Desktop, Mobile, Fullscreen

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16882