Implement Standalone Platform based on JLine3

Changes:
- Change completions so more info can be passed back including descriptions and command titles

- Add a new platform, Standalone, for standalone console applications

- Add `description` keyword to parsers so that a description can be provided during completion for platforms that support it (only Standalone at this time)

- Update documentation for new Standalone platform

Since Last Release:
* 1c09598 (HEAD, tag: v1.4.0) Implement Standalone Platform based on JLine3 [bundabrg]
Changes:
- Change completions so more info can be passed back including descriptions and command titles

- Add a new platform, Standalone, for standalone console applications

- Add `description` keyword to parsers so that a description can be provided during completion for platforms that support it (only Standalone at this time)

- Update documentation for new Standalone platform