Some dependencies are not available for python 3.7 anymore. Instead
of trying to support different versions of the libraries, we opt to
focus on the latest python version, and allow for CORE functionality
for earlier versions.
Update RDFlib to 6.1.1 (removed rdflib-jsonld, as it is deprecated)
Bumped minimum python version: 3.7 (as a result of RDFLIB 6)
Added ProxyFix to run behind nginx (Added --no-proxy to run without the fix)
Replaced http media links to protocol-agnostic links in playground
Enable CORS (via --enable-cors)
Update old urls (replaced *.cluster.gsi.dit.upm.es with *.gsi.upm.es)
