DATACMNS-596 - Introduced PersistentPropertyAccessor.

To be able to customize the lookup of bean properties by persistent store we now expose a getPropertyAccessor(Object entity) method on PersistentEntity. It returns a PersistentPropertyAccessor which is basically an interface with a simplified API of BeanWrapper.

Reduced the plain BeanWrapper to not perform any type conversion to be able to drop the ConversionService dependency. To compensate for that we introduced a ConvertingPropertyAccessor that takes a ConversionService and delegates to a standard PersistentPropertyAccessor and applies conversions if necessary.

Refactored client APIs to use the PersistentPropertyAccessor instead of referring to BeanWrapper directly. Deprecated BeanWrapper.create(…) for removal in RC1.