Changed SHOP_ORDER_EMAIL_SUBJECT setting into an email/order_receipt_subject.txt template.
This makes it possible to include some order info in the subject (such as order id).
Merge branch 'feature/receipt-subject-template' into develop

Conflicts:
	cartridge/shop/checkout.py
Changed SHOP_ORDER_EMAIL_SUBJECT setting into an email/order_receipt_subject.txt template.
This makes it possible to include some order info in the subject (such as order id).
Merge branch 'feature/receipt-subject-template' into develop

Conflicts:
	cartridge/shop/checkout.py
Remove newlines from the receipt subject, be it a configuration string or a rendered template.
Merge branch 'feature/receipt-subject-template' into develop