WIP: New module for serialisation to RDF

[jesper-friis]

Description:

Added a new module for serialisation an OTEAPI pipeline to RDF. The RDF produced by this module is much more readable and easier to work with compared to tripper.convert().

Planned tasks (some may be moved to new PRs):

• Implement serialisation to RDF using a JSON-LD context.
• Implement loading serialised RDF back to a dict representation.
• Check that save_dataset() works with the fuseki backend -- the fuseki backend must be fixed to handle (unescaped) embedded quotes.
• Check that load_dataset() works with the fuseki backend -- implemented load_dataset_sparql().
• Implement function that parses a YAML file to a dict-representation that can be serialised to RDF.
• Implement converter from OpenModel YAML format to new YAML format.
• Add documentation.

Type of change:

• Bug fix.
• New feature.
• Documentation update.

Checklist for the reviewer:

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand, including clearly named variables?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?

[jesper-friis]

Closing. Moved to tripper