Add constant for Credit Card payment type
This PR adds a constant to the MagentoOrder
class for the value CBS expects for credit card payments. For example:
$payment->setPaymentType(MagentoOrder::CREDIT_CARD_PAYMENT_TYPE);
$payment->setPaymentInfo($transactionApprovalCode)
Please review: @ahoffmann @weizhong-wang @lloyd-carter @KJOYNER