Fixes for new two-dash long command line arguments

- 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
- Cleanup obsolete code here and there

editor/run_settings_dialog.cpp

@@ -88,7 +88,5 @@ RunSettingsDialog::RunSettingsDialog() {
 	get_ok()->set_text(TTR("Close"));
 	//get_cancel()->set_text("Close");
 
-	arguments->set_text("-l $scene");
-
 	set_title(TTR("Scene Run Settings"));
 }