- New payment gateway 'bank'.
- Show gateway choice in payment forms.
- Paying by bank only supports manual.
- Changed braintree to only support automatic.
- Switching between gateways now also switches collection method for the
  subscription and any still-payable (e.g. 'created' and 'soft-failed')
  orders.
- The admin now has an action to bulk-mark orders as 'paid'.
- After completing the order, an email is sent with bank details.