DATAJPA-265 - Make it possible to configure auditing with Java Config.

Applied suggested changes from code review.
Removed implicit bean instantiation in AuditingBeanFactoryPostProcessor since the declaration of an explicit dependsOn clause for the appropriate entityManagerFactory-factory beans triggers the bean initialisation of ABCA early enough. Since an entityManagerFactory defined as an @Bean AnnotationBeanDefinition doesn't have a beanClass set by spring we check whether the given bean definition is compatible to a EntityManagerFactory.

Note that this depends on DATACMNS-389 (spring-data-commons #53) to be applied.