Inactive coupons must be displayed on completed orders

Problem: people use a coupon for a period of time, then an admin deactivates it. The orders that have been completed in the meantime must still display the disabled coupon correctly. Currently the label of the applied coupon is just empty and it is confusing why the amount is substracted from the price.

Proposed solution: always load all coupons for hook_commerce_price_component_type_info() so that even the inactive coupons are registered and get displayed on completed orders.