Allow for optionals in annotated methods

We should allow for optionals to be used in annotated arguments in place of nullable parameters. Example:

@Command("command [component]")
public void someCommand(Optional<SomeType> component) {
  // ...
}

We should be able to infer the type of the optional without any issues. We will need to consider the mapping between components and optionals both when parsing & constructing the command tree, but also when mapping the parsed values to the method parameters.

Start by tracing the code that parses annotated arguments and constructs the command tree, then follow the mapping from parsed values to method parameters. Done means an annotated Optional argument can infer SomeType and correctly map both present and absent command components.