Versioning of Docker images

[oleschwen]

We will likely use multiple versions of Docker images. To avoid confusion, we should use version numbers (probably more intuitive than, e.g., hash IDs) rather than a fixed name with varying images under that name.

TODO

• think about requirements
• think about implementation
• implement

[oleschwen]

Following #22, the image would contain the code for local training. We cannot easily use that code also for the swarm training (I wouldn't know how), but we could check before starting the admin console that the code version to be sent out by NVFlare matches the version contained in the image to avoid accidentally using non-matching versions. Do we want that?