Move setLaunchButton to setSideColumn for ObjectItem

Summary: Makes this a bit more flexible and allow UI to take over col-2 completely. Also cleaned up application search a little with tags

Test Plan: Review various pages, grep for callsites.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18021