Improvements to individual README.mds?

[jfpanisset]

Currently the jinja2 template which generates the README.md for each container lists "packages + implicitpackages" as one undifferentiated list. Would it make sense to explicitly separate the list of what comes from this specific container build vs what comes from the lower level containers it derives from?

On a related note (and I may be misunderstanding the nature of the hierarchy), the packages from ci-common don't seem to get listed: it would seem to be useful for instance to know exactly which version of clang / cuda / ... is in a container.