Tag docker versions based on the appveyor build version

[PandelisZ]

Currently the docker images are tagged mater, develop and then each commit also gets tagged with its commit id.

We should instead be tagging with the appveyor build number which appends itself as a tag:
https://circleci.com/docs/2.0/workflows/#executing-workflows-for-a-git-tag

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.