Update to create multi-architecture images - resolves #107

[carlosejimenez]

Reference Issues/PRs

Fixes #107 - makes the release_dockerhub.sh script suitable with multiple architectures specified using the same version tag.

What does this implement/fix? Explain your changes.

It changes the release_dockerhub.sh script to have more options (it also allows the option to change the docker username), and it allows multiple docker images built with different architectures to be attached to the same tag in docker hub using the docker manifest experimental CLI option.

Any other comments?

🧡 Thanks for contributing!