- Change interface to use (CommandSender, List<String> arguments)
- Use CommandArgumentDescription#name instead of "label" (to prevent confusion between command labels and arguments)
- Simplify command difference computation in CommandHandler (no longer consider argument difference)
- Move permissions responsibilities from command to permissions (remove some logic from CommandPermissions, add DefaultPermission enum to permissions package)
- Start possible interface for the future per-permission system implementations of permissions managers
- Create builder class for CommandDescription
- Remove redundant methods in command registration classes (e.g. certain validation is superfluous because we only instantiate the classes internally)
- Replace multiple occurrences where a field is directly instantiated e.g. with a list and then its value is overwritten by a constructor = redundant instantiation of objects
