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 ONE action: Open settings for a viewer whose plan covers it (no Get — see Extensions without Get), else the one plan affordance. See In-App Extensions.