support / showcase other triple stores

[marc-portier]

next to graphdb we should be able to use other triple stores as well

some to consider and test:

• https://jena.apache.org/documentation/fuseki2/fuseki-docker.html
• https://hub.docker.com/r/redpencil/virtuoso

challenges could be (comparable to what we did for graphdb)

• having a decent health-check
• ensuring a specific database per project gets created