Add a dedicated gateway plugin for SIBS_MULTIBANCO

SIBS_MULTIBANCO needs the following custom parameters:

• customParameters[SIBSMULTIBANCO_PtmntEntty]
• customParameters[SIBSMULTIBANCO_RefIntlDtTm]
• customParameters[SIBSMULTIBANCO_RefLmtDtTm]

UPDATE

We need a very special treatment, including a custom route, that shows a payment reference to the customer:

"we have to process the parameter that brings the payment ref: "pmtRef" and show it to the client. this is for get the references and showing them to client.
then, he said that the best is to supply and endpoint where it is triggered an operation of type RC (receipt) when there is a payment of a reference. IN that RC goes the referenceID (the transaction ID of the reference generation -PA- not the payment ref itself) and the merchantTransactionID that identifies the shopping activity
but I think we can also query with cron about the status of the payment"