Enhance @EnableSecurity to provide a default implementation of the GemFire AuthInitialize interface

This is an "improvement" to the existing @EnableSecurity annotation in SDG's Annotation-based configuration model to auto-configure an instance of Pivotal GemFire's AuthInitialize interface.

In GemFire's client/server topology, the AuthInitialize interface must be implemented by any (Spring (Boot)) GemFire cache client application when the GemFire cluster has Security enabled (i.e. a SecurityManager has been configured), which requires the client to be authenticated when connecting.