Check for toJson() in option if Handler or AsyncResultHandler

Check that `toJson()` method is in Options if used in `Handler<>` or `Handler<AsyncResult<>>`

https://github.com/vert-x3/vertx-codegen/issues/16


Oops, sorry, I shouldn't have pushed that. I tried to use this for `method(SomeOption option);` and check for a JsonObject constructor. But as said before, the JsonObject constructor is a requirement anyways.