Use the git skeleton file. Apply changes from the new hooks.

To have a common .gitlab-ci.yml.

I'm moving some services to ns4, some will remain on host01. I'm
branching to have specific deployment for each host. So have a minimal
and generic master branch so common changes will be done there and I'll
rebase the other branches on top of it.

- Use common pre-commit snippet for Docker projects.
- Use GitLab CI template for pre-commit job.