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

Introduces the necessary infrastructure in form of JpaAuditingRegistrar to configure Auditing with JPA via Annotation config. The JPA Auditing feature can be enabled by annotating a configuration class with the EnableJpaAuditing annotation.

Note that this depends on DATACMNS-389 (spring-data-commons #53) to be applied.
Partially based in PR: #21 with some modifications.