- Fixes some single-dash leftovers that were missed in the previous commit
- Reorder the help output for clarity, and document missing options
- Drop obsolete options: --noop, --pack, --editor-scene, --level, --import, --import-script, --no-quit
- Improve error message on malformed arguments and do not display help on error
- Always use long form of arguments when starting a new Godot process from C++, for clarity and easy grepping
- Cleanup obsolete code here and there