Add an Alternative "Soft" IBAN Validation

[elcapo]

The actual IBAN validation is way too strict. We should create a second one (isValidIBANMaybe) that verifies the check digits and makes sure the first two digits are characters, but that doesn't verify the length of the string against the list of known lengths and that doesn't need the country to be recognised as a SEPA country to return true.