Implement Docker container

[stdevel]

Is your feature request related to a problem? Please describe.
During fresh installations it could be a benefit having a pre-built Docker container that contains the katprep commands and all the necessary Python module dependencies. Especially on legacy distributions, installing katprep can be painful.

Describe the solution you'd like
Serve a Docker container that serves the katprep utilities, e.g. like: https://hub.docker.com/r/vmware/powerclicore

Describe alternatives you've considered

Additional context
Open questions:

• how to deal with files needed for processing automation, e.g. authentication containers, snapshot files and reports?
• implement a katprep shell to avoid typing long Docker commands to execute the particular katprep sub-commands in a dedicated manner (see also issue Simplify katprep commands #101)