Added check for legal persons in cf

"cf" stands for Codice Fiscale (Italian fiscal code card). For legal persons (e.g. corporations) it comprises 11 numeric-only characters 

Source: https://en.wikipedia.org/wiki/Italian_fiscal_code_card
fixed integer comparison (strict)
Added test for legal persons in ItValidation::cf
Merge pull request #79 from fiblan/patch-2

Added check for legal persons in cf (ItValidation)