Non-static inner classes support

By the nature of non-static inner classes, they cannot have a default non-argument constructor which makes not possible to deserialize them using default mapping. The spec has to be changed in a way that non-static inner classes support is removed or non-static inner classes are supported only for serialization.
See discussion on Yasson issues tracker:
https://github.com/eclipse/yasson/issues/49

Start by reading the issue discussion and the linked Yasson issue 49 to understand the compatibility and deserialization constraints. Identify where the JSON-B specification addresses non-static inner classes; done means the specification position is resolved and documented consistently.

Written by the indexing model from the issue text.