move non-novice episodes / concepts to intermediate+ repo

[mr-c]

https://github.com/common-workflow-lab/cwl-intermediate-tutorial

[douglowe]

I've started dividing (what I think are) the intermediate episodes into my copy of the repository: https://github.com/douglowe/cwl-intermediate-tutorial. The lessons (currently) are:

• CWL recap
• dynamic workflows
• scatter
• nesting workflows
• including shell scripts
• customize
• running on HPC
• running on cloud

Probably the last two should be (very) optional episodes though, depending on the resources available for the lesson.