Fix for the problems identified in issue #4892
Bugfix: admin-ui order summary no longer uses gift card total from order when displaying how much has been withdrawn from each giftcard.
Bugfix(?): no longer keep applying gift cards (at 0 value) when sufficient balance has been reached
Feature: multiple giftcards are now applied in ordered fashion. First by end_date (supports null), then by remaining balance. In order to ensure that customers ends up with as long lasting and few remaining gift cards as possible after the transaction.
