Update github sync workflow, switch to docker, add gitlab CI for building docker container and push to registry

Created by: bernt-matthias

In order to make this work Settings -> Secrets -> Create new Secret add HZDR_ACCESS_TOKEN (I will send the token to @mai00fti on another channel)

This PR implements the following:

• the github actions workflow that syncs to HZDR will be triggered when a new release is created (with a new tag).
• there an gitlab workflow will run that
  • builds a docker container tagged with the git tag (eg vx.x.x),
  • runs the tests (pytest and dfpl --help at the moment), and
  • pushes the container to the registry and updates the container with the latest tag in the registry

The changes to setup.py will lead to the creation of /bin/dfpl on installation, so running with python -m dfpl is not necessary anymore (but still possible).

Note there are two changes in python scripts that appeared necessary to me. Please review particularly careful.

From now on releases should be done as follows:

1. change version in setup.py
2. git commit setup.py -m 'release vx.x.x'
3. git push upstream master

On the github page a new release can be created. For this create a new version tag (vx.x.x) and add sufficient description.

TODOs:

• The README.md mentions run-all-cases.sh. The data used there seems not available.