Respect phriction.enabled in config
Summary: Eventually we'll have a real "uninstall" sort of thing, but until we do we should keep respecting this flag.
Test Plan: Disabled the flag, saw Phriction vanish from the application list.
Reviewers: btrahan, vrana
Reviewed By: btrahan
CC: aran
Differential Revision: https://secure.phabricator.com/D3724