feat: improve smart view for OAI-PMH

DLCM-Access/src/main/resources/xslt/datacite2oai_dc.xsl

DLCM-Model/src/main/resources/xslt/dlcm_oai2.xsl

...odel/src/test/java/ch/dlcm/test/tool/AbstractXMLTest.java

DLCM-Model/src/test/java/ch/dlcm/test/tool/MetadataTest.java

DLCM-Model/src/test/java/ch/dlcm/test/tool/XSLTest.java

DLCM-Model/src/test/resources/dlcm/dlcm_datacite-3.0.xml

...-Model/src/test/resources/dlcm/dlcm_datacite_date-3.0.xml

DLCM-Model/src/test/resources/dlcm/dlcm_mets-3.0.xml

DLCM-Model/src/test/resources/dlcm/dlcm_premis-3.0.xml