Add some magic getters

Some magic getters about Code and Intl/CreditCardNumber.

See #4
Start some work about ISAN and VISAN codes

Statr implementing ISAN.

See #3
Formatable implementation and unittesting
Magic getters for ISAN
Missing parent method call
Added VISAN
Magic getter version fo VISAN
URN and new example for UT
Additional unit testings for VISAN
ISMN stuff and some unit testing added