Review of INTERMAGNET JSON-LD

[rweigel]

The following is ready for review:

• Single observatory, all datasets: https://hapi-server.org/meta/relations/INTERMAGNET-aae.jsonld

• All observatories, all datasets: https://hapi-server.org/meta/relations/INTERMAGNET.jsonld

The generation code has been removed from this repo and is now in relations.py.

An easy way to visualize the single observatory case is to copy/paste into https://jsoncrack.com/editor.

[rweigel]

Added WDC relations as well. See https://hapi-server.org/meta/relations/