Added a discount_type field to orders, so  discounts may be distinguished from each other.
Merge branch 'feature/loyalty-discounts' into develop
Made null or empty total titles fall back to default labels; added a note about the discount_type field (from the loyalty-discounts branch).
Merge branch 'feature/configurable-order-totals' into develop
Moved discount code session logic to the model to match the new interface and save its title; decided to use unicode(self) for order totals labels -- this should make adding some more elaborate title logic as simple as overriding a method.
Merge branch 'feature/loyalty-discounts' into develop

Conflicts:
	cartridge/shop/forms.py