More than one dataset indentifier

[VeronikaKusova]

This issue comes from the GeoDCAT-AP 3.0.0 pilot.

Not a bug, just a warning of a possible problem.

If there is more than 1 dataset identifier (gmd:identificationInfo/../gmd:identifier) in the ISO metadata, only the last one is used in RDF (after the XSLT).
For example we use one identifier as identifier(product code) in our organisation and another one as the dataset identifier for inspire. And the main identifier (INSPIRE identifier) is the first one.