Updates for DataCite Metadata Schema 4.5

[jesusbagpuss]

Announcement: https://datacite.org/blog/introducing-datacite-metadata-schema-4-5/
Details: https://schema.datacite.org/meta/kernel-4.5/

The new publisherIdentfier attributes are most relevant:
<publisher xml:lang="en" publisherIdentifier="https://ror.org/04z8jg394" publisherIdentifierScheme="ROR" schemeURI="https://ror.org/">Example Publisher</publisher>

Changes to the documentation are detailed here: https://datacite-metadata-schema.readthedocs.io/en/4.5/introduction/version-update/#documentation-changes . I think there are a few aspects around 'relatedItem' that are relevant to the EPrints integration.

Also need to update SchemaLocation in cfg/cfg.d/z_datacitedoi.pl