Add more info to cli help

[rcannood]

Describe your changes

This PR adds more info to the CLI help.

Type of Change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• New functionality (non-breaking change which adds functionality)
• Major change (non-breaking change which modifies existing functionality)
• Minor change (non-breaking change which does not modify existing functionality)
• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

Checklist

Requirements:

• I have read the CONTRIBUTING doc.
• I have performed a self-review of my code by checking the "Changed Files" tab.
• My code follows the code style of this project.

Tests:

• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.

Documentation:

• Proposed changes are described in the CHANGELOG.md.
• I have updated the documentation accordingly.

Test Environment

[Grifs]

I see that this would be useful for the developer of a component, but it might be confusing for the person who has to run the components.

Some minor remarks added too.

[Grifs]

Is this the right section to document environment variable usage?

[rcannood]

Well at the moment we don't document environment variables at all. But perhaps it should be listed as a separate section. Do you think that's better?

[rcannood]

I see that this would be useful for the developer of a component, but it might be confusing for the person who has to run the components.

That's also true. Maybe I'll get rid of the additional information, but do add some docs about VIASH_TEMP?