Implement SPARQL queries for CQs

To validate that the Flint ontology supports the in-scope CQs, we want to write SPARQL queries showing how to get the necessary information.

@MerleBeaujon will look into this. Some pointers / inspiration:

• Feel free to make sub-issues if that helps break up the work
• Flint CQs are getting a revamp (some changes, mostly rephrasings); see #53 (closed) and the MR. I recommend to base the work off of that branch so that it is easier to merge when things are done.
• See the Source ontology CQs for some examples
  • A rich example is this one; there I used VALUES to indicate the example values that the CQ assumed with phrases like "Given a source, ...". I also used the ex: namespace for the examples. And I wrote relatively many/long code comments, to explain how the query relates to the CQ.
  • I suggest to name the file the same as the CQ name