Add JSON path navigation support

[beikov]

Splitted off of #841 for the path navigation support.

I'd like to allow dereferencing a json attribute via normal path navigation I.e. jsonAttribute.person.age

In order to make this happen, we need a json metamodel in java that we can query to know what to cast a result to and to decide if a specific navigation operation is allowed. Maybe we could also support that without a model but then the user would have to do casts of the final values. I was thinking about using the colum definition or a custom annotation on the entity attribute to detect JSON typed attributes.

Selecting sub-objects of the JSON type should be possible by making use of a JSON binding provider in an internal ObjecBuilder.

This is blocked by #765 which will enable us to model foreign model structures and allow to easily de-reference it.