Parse creators from dcterms:creator vCard4 annotations

[dyrpsf]

Summary

This PR extends SBMLRDFAnnotationParser so that creators written using the newer
dcterms:creator + vCard4 format (as produced by libSBML) are parsed into History /
Creator objects, in addition to the existing support for the legacy
dc:creator + vCard/v1 format.

Concrete changes:

• readRDFHistory now also looks for dcterms:creator elements in the dcterms
  namespace (JSBML.URI_PURL_TERMS) and calls readCreator on them, so both
  <dc:creator> and <dcterms:creator> blocks are handled.

• readCreator(...) still supports the original vCard pattern:

  • vCard:N → vCard:Family, vCard:Given
  • vCard:EMAIL
  • vCard:ORG → vCard:Orgname

  but now also falls back to vCard4 when those nodes are not present:

  • vCard4:hasName → vCard4:family-name, vCard4:given-name
  • vCard4:hasEmail
  • vCard4:organization-name

  The vCard4 namespace used is http://www.w3.org/2006/vcard/ns#.

This addresses creators that are written using vCard4 as in
sbmlteam/jsbml#270, so that
History.getListOfCreators() returns the expected Creator instances.

Verification

• Built JSBML and ran the core tests with Java 11:

  mvn test -pl core -am

The jsbml-core tests pass, so the new parsing logic does not break the
existing test suite.

Fixes #270

[draeger]

It would be better to collect String literals as public static final String constants; possibly an enum could be created. I'd suggest avoiding keywords in the source code, as this can be hard to maintain if, for instance, typos occur.