Non-static inner classes support

[jansupol]

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:
eclipse-ee4j/yasson#49

[jansupol]

• Issue Imported From: https://github.com/javaee/jsonb-spec/issues/68
• Original Issue Raised By:@m0mus
• Original Issue Assigned To: Unassigned