#25 UPC/EAN: Make printing of check digit in human-readable text configurable

[Daniel Gredler]

I need to be able to omit the check digit from the human readable text when printing UPC-A bar codes. This patch removes the current use of "instanceof" to make this decision, and replaces it with configurable boolean properties on the UPC and EAN barcode beans (with sensible defaults that match the spec and today's behavior).