Added Docker labels and tagging Docker images with Git tags

This merge request adds labels to Docker images produced by CI and manual invocations of build_instance.sh script.

It also updates the CI to check if the pipeline is run for a Git tag - and if so to additionally tag the resulting Clive Docker image with that Git tag (eg: https://gitlab.syncad.com/hive/clive/-/jobs/1001077).

This creates a one-to-one relationship between Git And Docker tags - although it's still possible to arbitrally add Docker tags by pulling or building an image locally, tagging it and pushing it to the repository.