docs: cleanup / refactor cli doc
docs: cleanup / refactor cli doc

More improvements can be made, but this makes a start on cleaning up
this page:

- Reorganise configuration file options into sections
- Use tables for related options to make them easier to find
- Add warning about the config file's possibility to contain sensitive information
- Some MarkDown touch-ups (use "console" code-hint to assist copy/paste)

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

thaJeztah/cli,cpuguy83/cli,cpuguy83/cli,docker/cli,thaJeztah/cli,docker/cli