Update dockerfiles of node and builder to enable futher CI / CD automation

Description

The builder image should be able to check if the current version should also be tagged as "latest" in the docker registry. The node image should be able to launch a command depending on the reachability of another hosts service (eg. netcat scan)

Explanation

Our advances in automated publishing docker image require that the "latest" tag is given to the latest version released (semver). As of minimal-connector#6 this is implemented but every time curl and jq packages have to be installed. The installation and the scripts should be moved into the image.

As we update our docker-compose file version beyond 2.x we loose the ability to use healthchecks as we do them now, to wait for a service to become available. It's recommended to move this functionality into the image. Putting the rather simple https://github.com/eficode/wait-for into the node image should be sufficient.

Dependencies, issues to be resolved beforehand

none