Introduce ``bda.plone.payment.interfaces.IPaymentSettings``. Implement ``available`` and ``default`` properties on ``bda.plone.payment.Payment`` using settings from ``bda.plone.payment.interfaces.IPaymentSettings``. Add missing ``pid`` attribute to ``bda.plone.payment.Payment``. Remove ``available`` and ``default`` attributes from ``bda.plone.payment.cash.Cash``, ``bda.plone.payment.debit_order.DebitOrder``, ``bda.plone.payment.invoice.Invoice`` and ``bda.plone.payment.six_payment.SixPayment`` since they are provided by base class now.