Add support for 2013 extension of Irish PPS Numbers

Support the new extra letter at the end of PPS numbers (weight=9), while maintaining compatibility with the old format.
Add a few test PPS numbers, keep `ie` coverage at 100%.

References:
- https://www.welfare.ie/en/Pages/PPSN.aspx
- http://www.citizensinformation.ie/en/social_welfare/irish_social_welfare_system/personal_public_service_number.html