PDF error wiki needs to be updated

[samalloing]

The last error on the PDF wiki page is pdf-hul-154 and there are more errors already in the code

[carlwilson]

Thanks for this @samalloing. I think we need a few things here:

• a process for ensuring that all new error messages are on the wiki;
• ensuring that all new error messages/codes are in every translation resource file (even if this is just the default original at first); and
• automated tests for the above.

This isn't tied to a release as such and the JHOVE interest group might have a role to play.