Resolve "add more helpful information on `meltano install --help`"

Merge Request Checklist

• Link to an issue
• Include the proposed fix or feature
• Include and update tests for the modified code
• Include a documentation change
• Add a CHANGELOG.md entry in the Unreleased section

Once your merge request is complete, please assign it a Meltano maintainer for review cycle. Once the review cycle finished, the reviewer shall approve the merge request so it can be merged by any Meltano maintainer.

Closes #666 (closed)

Adds more useful information to meltano --help and meltano install --help based on the feedback in !712 (comment 189376730)