Publish website-builder and tooling images once per week

The two images website-builder and tooling are currently published to Docker Hub only manually. Let's set up Jenkins jobs for doing so on a weekly basis, so that for instance all the installed packages are up-to-date. The following things should be done:

• Set up the Jenkins jobs; let's use the "latest" tag for these continuously updated images
• Update the Fedora and kafkacat (renamed to kcat lately) version for the tooling image
• Bonus: add kcctl to the tooling image; while there is no installation package for it yet, early access builds can be obtained from GitHub