Add formatter implementation for DCAT supporting turtle and json-ld formats

[josegar74]

This change request adds a DcatFormatter class that uses the XsltFormatter to create RDF/XML for DCAT formatters and allows to convert the result using Jena to Turtle or JSON-LD:

• RDF/XML: http://localhost:8080/geonetwork/srv/api/records/da165110-88fd-11da-a88f-000d939bc5d8/formatters/dcat
• Turtle: http://localhost:8080/geonetwork/srv/api/records/da165110-88fd-11da-a88f-000d939bc5d8/formatters/dcat?output=turtle
• JSON-LD: http://localhost:8080/geonetwork/srv/api/records/da165110-88fd-11da-a88f-000d939bc5d8/formatters/dcat?output=jsonld

Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation

[CLAassistant]

All committers have signed the CLA.