ISO/IEC 7812 card number support

[marcwrobel]

Add ISO/IEC 7812 card number support.

[jycr]

It would be better to include this feature in another library.
In a pure SEPA processing platform, we does not need to deal with Credit Card number.

[marcwrobel]

@jycr, thank you for your feedback.

JBanking is meant to address general banking concerns, it is not only a library for SEPA. So I still think this feature can have its place in this library.