Feature/container

[atanikan]

• Moved Path for containers from inside datascience to outside for easier access (as container are more general purpose)
• Updated documentation of container for Sophia and Polaris
• Updated documentation for using Python on Sophia

[felker]

Nice use of https://facelessuser.github.io/pymdown-extensions/extensions/snippets/#snippet-sections ! Others should start using this feature

user-guides/docs/polaris/containers/containers.md

Line 102 in 2e919e0

--8<-- [start:commoncontainerdoc]

There are a few leftover stylistic inconsistencies (I really dislike seeing "Tensorflow" instead of "TensorFlow" 😄 ), and I think the referenced https://github.com/argonne-lcf/container-registry could use a big update somday soon, but looks good to me now.