DATAMONGO-569 - Improved AbstractMongoConfiguration.

AbstractMongoConfiguration doesn't expose a Mongo instance anymore until you explicitly make it one by annotating the implementation method in the configuration sub lass with @Bean.

Removed the custom call to MongoMappingContext.initialize() as Spring call the lifecycle method for us anyway.
DATAMONGO-682 - Performance improvement for mapping hotspots.

This commit includes the MongoDB specific parts for the mapping subsystem performance improvements. Reworked PerformanceTest to output more reasonable numbers.

Heavily inspired by Patryk Wasik's contribution at https://github.com/SpringSource/spring-data-mongodb/pull/37.

GitHub PR: #37