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[bot]]

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