PPSRNZ Security Enquiry; better handling of non-ASCII characters

The PPSRNZ Security Enquiry does not handle diacritical or other non-ASCII characters. For example, sending data that includes accented characters will return the server error "Internal Server Error".

Diacritical characters sent in Plate data are now converted to basic Latin equivalents, e.g. "ÁBC123" becomes "ABC123". Chinese and other non-Latin characters are removed from Plate data.

Diacritical characters in VIN numbers now produce validation errors, e.g. "Invalid character 'Á' in VIN".