R1:d0c09ef8676b

Add a way to get to the home dashboard on mobile

Summary: Fixes T5320. Adds a "Home" application at the top, for mobile-only.

Test Plan: See screenshots.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5320

Differential Revision: https://secure.phabricator.com/D9509