Small updates to "help"

Help-related:

- FEATURE: can use `desc` field with arguments
- removed unused `help.bannerFor()`
- updated some JSDoc
- option defaults no longer display if default value is an empty string
- rewrote unit tests for `help.help()` function
    - the old tests made it difficult to debug since Mocha would only report truthiness
    - using the updated method, we now compare strings and can easily see any differences as reported by the assertions
    - I also elected to ignore extra whitespace here, because I want to test the content; not the `text-table` module's output.

General:

- removed unused vars in `base.js`
- updated JSDoc tags in `base.js`
- simplified a boolean expression