[WIP] Config labels

1. Not sure. I'd have to try..
2. Yes, I thought setting Labels to the objects that doesn't define any such field (eg. Template, Config, Image, ImageRepositoryMapping etc.) would be a bad practice. I think the problem would grow drastically, if I had to loop over the the objects recursively. And I guess we might be doing this eventually. Then, all of the generated json Objects would have the "Labels" field, even the "Labels".