Add goal "push" (or "deploy") for sending a data container to a registry

[rhuss]

As we now have a way for create data docker container, it would be nice to not use it only for linking this into the app-server container during integration testing but also to offer a possibility to push it to a registry so that it can be used as a deployment mechanism.

[rhuss]

For security aspects, it would be cool, if we could stay as close as possible to the Maven security approach.

I.e. in principle it should be possible to createn an ow wagon for pushing to a registry so that credentials can be kept in the settings.xml

A wagon would also super nice for pushing to a Docker registry during deployment: mvn deploy:deploy could use the docker wagon which in turn creates a docker image on the fly (with all artefacts).

Still have to learn about the Maven wagon approach, though.

[rhuss]

I implemented it now straight forward (was hard enough ;-). Released in 0.9.6