Shipping Rate Options on Checkout

[EvanSchisler]

We need to actually display the rate options on checkout so a user can pick them and an "active" one can be selected. Talk with fbailey about listing structure as I believe he has already started on that, but we need the concept of a list of rates so that we can have all of them attached to a shipment, but then one can be selected by the customer. The same logic will hold true for the other types such as box, label etc. but will likely be backend only.