Iterate Format Toward CWL

After 20.01 branches - add ``profileVersion`` and iterate toward CWL:

- Allow step_type, tool_id, etc... to be inside of ``run`` - maybe ``GalaxyToolReference``.
- Allow ``doc`` to be a list of comments (re-use Documented from cwl's Process.yml).

...

No implementation files or tests are named. Start by reviewing the 20.01 branches and comparing the existing format with CWL's Process.yml; done means adding profileVersion, supporting step_type and tool_id inside run, and allowing doc to contain a list of comments.

Written by the indexing model from the issue text.