Summary: This does some backend cleanup of the tile stuff, and some general cleanup of other application things: - Users who haven't customized preferences get a small, specific set of pinned applications: Differential, Maniphest, Diffusion, Audit, Phriction, Projects (and, for administrators, Auth, Config and People). - Old tile size methods are replaced with `isPinnnedByDefault()`. - Shortened some short descriptions. - `shouldAppearInLaunchView()` replaced by less ambiguous `isLaunchable()`. - Added a marker for third-party / extension applications. Test Plan: Faked away my preferences and viewed the home page, saw a smaller set of default pins. Reviewers: chad Reviewed By: chad Subscribers: epriestley Differential Revision: https://secure.phabricator.com/D9358