Spring data JPA support

[javier-godoy]

Experimental implementation that leverages JpaSpecificationExecutor in order to support spring-data repositories from commons-backend services.

The implementation depends on commons-data-impl in order to reutilize ConstraintTransformerJpaImpl

Example:

public interface MyEntityDao 
	extends CrudRepository<MyEntity, Long>, 
	JpaSpecificationExecutor<MyEntity> { }

public class MyEntityServiceImpl
	extends JpaCrudService<MyEntity, Long>
	implements MyEntityService {

	@Autowired
	@Getter
	private MyEntityDao crudRepository;

	@Autowired
	@Getter
	private MyEntityDao executor;

	@Override
	protected Long getId(MyEntity entity) {
		return entity.getId();
	}
	
}

[mlopezFC]

Maybe it would be a good idea to rename the new module to commons-business-spring-impl
What do you think?

[mlopezFC]

LGTM