Template for Docker containers

Now that both DPPS and ACADA are packaging things in Containers, having a standard template for a container or a base container itself would be useful, along with guidelines on how to build them.

This should also include optionally a conda installation inside the container for pipeline software, so that the container can contain one or more conda environments.

• Should be in common with ACADA (maybe)
• common linux distro, common way of installation, etc. Common place to put conda repos,
• where to put containers when done (GitLab, Harbor, ...?)
• same issue for conda envs (need some management in where they are created, updated, etc)