Support for jMolecules' Association type

[odrotbohm]

It would be cool if Spring Data's object mapping infrastructure supported jMolecules Association type discovering it as logical association and automatically converting it into its identifier type and the underlying primitive value respectively:

class Aggregate {
  Association<OtherAggregate, OtherAggregateIdentifier> association;
}

class OtherAggregateIdentifier implements Identifier {
  UUID id;
}

The former needs PersistentProperty.isAssociation() to be made aware of the type. The latter can be implemented by adding the Converter implementations available in jMolecules jmolecules-spring artifact.