Setting attribute label to <none> should work for all contexts

Currently, setting the attribute label to <none> will only affect the display of the attribute on the product page. It does not affect the display on /cart, /cart/checkout, or /admin/store/orders/%oid. On these other pages, if the label is set to <none>, the attribute name is displayed instead of the label.

While this behavior may be changed through standard Drupal theming, it would be better to have <none> work in all contexts where the attribute label may be displayed.