Combined loyalty, facebook and voucher discounts (facebook and voucher classes rely on changes from the loyalty branch).

Merge branch 'feature/voucher-discounts' into feature/discounts-combined

Conflicts:
	cartridge/shop/defaults.py
Added a discounts toggle to enable application-specific order-based discount control. Removed some redundant code.
Merge branch 'feature/discounts-combined' into develop

Conflicts:
	cartridge/shop/defaults.py