ulo-storage-endpoint: add DCTerms.java

Created using

 rdf4j-schema-generator/rdf4j-schema-generator -f application/xml \
   -c LOWER_UNDERSCORE -u http://purl.org/dc/terms/ -name dcterms \
   dublin_core_terms.rdf DCTerms.java

with the rdf4j-schema-generator [1] and the dcterms RDF file [2].

[1] https://github.com/ansell/rdf4j-schema-generator
[2] https://www.dublincore.org/specifications/dublin-core/dcmi-terms/dublin_core_terms.rdf