Nexmark queries
This merge will add the nexmark queries to the project, as well as the sanity check scripts and the latency calculation scripts.
After this merge, the branches performance/latency, benchmark/nexmark_new_sellers and benchmark/nexmark_generator can be deleted (they were wrongly added, just leftovers from local development)
It would also be good to merge the branch feature/user-friendly-verticies in the master branch as well (after updating the readme and adding the copyright headings to the different files).