Solution for ES creation of ids

So I think this could be a solution for entities whose ids will be generated by elasticsearch. It works with multiple entities being stored. I see no problem to represent the id generation of ES in this lib, I think we have to support it.

For this solution there is honestly one little downside: You have to name your entity's id ``$id``. But this is nevertheless the case, as ``getId()`` also expects the entities to name it something like ``$id``. And to be honest: Who does not name it ``$id``?

I still don't know what is wrong with this spaces. I use PHPStorm. This is not for all files of the lib, just for a few. Other files work correctly. Maybe this is some git issue?