DATAREST-200 - Embedded associations get rendered again.

Removed too strong guard that prevented managed but not-exported types to be rendered at all.
DATAREST-199 - Tweaked unmarshalling of JSON payloads.

The BeanWrapper used to set and get values of entities now gets a autowired ConversionService applied. Simplified collection and map creation by using Spring API. Added test case to update an entity with an embedded collection.