Updated mmd-to-geonorge to pick up only compliant values of spatial representation (only vector and grid are valid entries, other mmd supported entries are only internal)
Update mmd-to-geonorge publication date (this is not part of #226 , but while testing the changes I've noticed that publication_date is the xsd is not forced to be a xs:date, only xs:string, documentation says we expect a date (not datetime), but several mmd records are not following this and provide datetime instead)
Closes #226