Help layout improvements

Suggesting couple of improvements for help layout

1. In case the option has many suggestions, the first column in layout becomes wide and layout is not very readable. Consider some shortcuts for these case, example,
Actual: `--my-option `
Suggested: `--my-option ` or `--my-option ` + list all possible values in descriptions etc.

2. Consider better representation when option default value is set to empty string.
Actual: `[default: ]` which is confusing as might be read as no default value.
Suggested `[default:]` or similar