Improve Directory XML file quality

[allikah1]

I would propose that Peppol Directory XML dump file is either containing a flag regarding if document type under discussion belongs to Peppol supported list (meaning it is standard) or it ain't standard type.

[Philip Helger]

Is part of the 0.8.5 release, but only in the full XML export.
The doctypeid element was extended:

• Either the attribute non-standard with value true is contained or
• the attribute displayname and the attribute deprecated