[next] add help() func to test runner

[jschmid1]

• rely on a doc_template living in doc.py This will make sure to have a consistent way of writing help texts for all our runners.

• use pydoc's pager() functionality to use the systems default pager

[jschmid1]

This is an easier approach as opposed to writing .rst documentation that will be exported to .pdf, .man, .html and other useful formats.