Make RDF more readable

[graybeal]

When displaying the RDF output in the instance, and optionally when exporting it, make it more readable. Particular recommendations:

• capture common paths as prefixes;
• make presentation window expandable;
• break lines (with indentation of follow-on lines) at spaces
• offer TTL and other nicer formats for RDF
• If feasible, separate sections (and elements?) with spaces and/or comment lines (could use form section headers and element titles to label the RDF sections)

Reference https://github.com/LD4P/requirements/issues/160 and https://github.com/LD4P/requirements/issues/159.

[willrett]

Common prefixed task is here: https://github.com/metadatacenter/cedar-template-server/issues/39. Just put in 2.2.

This can likely be done by simple configuration of the existing JSON-LD to RDF library. The other tasks might involve a significant amount of custom work so putting in backlog for the moment.