Added missing currency and language codes

I've added all the missing currency and language codes, as expressed in the [official italian documentation](https://www.gestpay.it/gestpay/doc/specifiche-tecniche/professional/gestpay_specifiche_tecniche_sicurezza_con_crittografia.pdf).

To make the code more robust, I added the default language codes, using 2-letters and 3-letters codes taken from the [ISO 639](http://en.wikipedia.org/wiki/List_of_ISO_639-1_codes) standard.