Add revert mechanism to promotion actions
Add relation Promotion-PromotionSubjectInterface
Change the way promotions are applied/reverted
Add specs
Optimize the way promotions are retrieved
Make Order-Promotion bidirectional
Give relation ownership to Order
Remove unused repository method
Implement revert on ShippingDiscountAction
Remove unused use statements
Merge pull request #692 from winzou/promotion-revert

[Promotion] Add revert mechanism to promotion actions