WW-3952: Credit card validator

[lukaszlenart]

Implements a credit card validator
WW-3952

[lukaszlenart]

This is ready for review

[cnenning]

I hope the regex is stable 😉

[lukaszlenart]

I hope the regex is stable

What do you mean by that? I have used this http://www.regular-expressions.info/creditcard.html

[cnenning]

How often do credit card companies change their number-patterns in a way that the regex needs to be updated? 'guess it is rare enough.

[lukaszlenart]

Good question... I have used those random card numbers in tests and looks ok (but we will see) https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm

[cnenning]

If patterns change users have another reason to upgrade to latest struts 😆

[gregh3269]

Last time I did some credit card validation, I needed to use a java script version as the payment process obscured the field names by not having the "name" attribute (so it was not obvious when these were sent over https) and I was unable to do server side validation.