Add version management and release notifications

[laurianvm]

Add versioning to the k-gap framework; And think about a way to include release notifications when new versions become available

[marc-portier]

Partial provisions in the Makefile already cater for some injected BUILD_TAG already exist.

remaining things I see todo:

• document how to apply semver.org release numbering
• describe how to relate that to github release declaration
• have the .github/workflows/docker-images.yml use release tag info and pass it down into the make process
• consider documentation release & publication on open-science.vliz.be/kgap ? (see separate issue #2 for that)
• also allow the #1 work to work with releases:
  • e.g. ask for which kgap release one would want to use
  • e.g. provide an easy mechanism (config in .env? what required docker pull commands?) to have kgap-using-projects to alter / upgrade releases ...

[marc-portier]

for future findability -- solution for this was part of #19