Add testing and CI

[tcojean]

It should be possible to add Gitlab CI with a few test cases to this tool itself so that we can ensure it still does its job when updating it without manual involvement and while not making our entire Ginkgo pipelines fail during testing.

To do so, we would need to register a test/beta runner on an HPC machine. A problem is that for now, BwUni seems to only support one runner per user (from previous tests)?

Managing the runner's script update on the server-side might be a bit more tricky without relying on ssh, maybe a simple cron job would be sufficient with a trigger from the server-side when master is updated.