Move controller request parsing to a utility class
Bring in product properties partial from spree.
Set the position based on the order from the request.
Display product properties properly on the frontend.

Some of this logic is better placed in a controller, however, by doing
it here we don't have to override the products controller. Ideally, a
draper decorator would fit well here for evaluating
properties_by_category but spree doesn't have it listed as a dependency
and we want to avoid introducing new ones.
Basic frontend styling to support categories.