Add Support for JCB and Diners Club Cards

- Update card validation to use regular expressions to validate card
numbers instead of simple 2 digit prefixes.
- JCB cards use standard 16 digit numbers. Diners Club numbers are 14
digits which are formatted as 4-6-4 so we can reuse the Amex formatting
which is 4-6-5.
- Add JCB and Diners Club card images as well as the original SVG
assets used to generate them.