Update parser with latest Eircode spec information

Based on the document “Prepare your business for Eircode” the following
changes have been made:

- Added ‘B’, ‘G’, ‘J’, ‘L’, ‘M’, ‘Q’, ’S’, ‘U’, ‘Z’ as disallowed
letters
- Removed ’N’ as a disallowed letter
- Removed ‘0’ and ‘1’ as disallowed numbers

I also changed the example Eircode ‘A65 R2GF’ to ‘A65 F4E2’ since the
former is no longer a valid Eircode according to the latest spec
information.