Person app tabs

The Store's contributions to the person app (/{user}/Settings). Each child is a UiContribution node with context: PersonApp; its id is the tab id (/{user}/Settings/{id}), and it renders a Store layout area. Extensions is the shelf of in-app extensions of the person app — every package declaring hostedIn: "{user}/Settings", each with its own Get / Buy / Uninstall. See In-App Extensions.