DATAMONGO-348 - Add support for lazy loading of DbRefs.

Introduced DbRefResolver interface in order to be able to abstract how a DbRef is resolved that is used in MappingMongoConverter#doWithAssociations. The present behaviour was to resolve a DbRef eagerly. This functionality is now implemented by EagerDbRefResolver. In order to support lazy loading we have to provide some means to define the desired loading behaviour. This can now be done via the "lazy"-Attribute on @DbRef which defaults to false.
If the attribute is set to true the LazyDbRefResolver is used to create a Proxy that eagerly loads the required data on demand when one of the (non-Object) proxy methods is called. MongoDbFactory now exposes a MongoExceptionTranslator that is now used by the MappingMongoConverter and MongoTemplate.

Introduced a DelegatingDbRefResolver that can delegate to a DbRefResolveCallback in order  to perform the actual DbRef resolution.
We now use cglib-proxies if necessary if the referenced association is a concrete class.

Added unit tests for lazy loading of interface types, concrete collection types and concrete domain types. Exposed state from LazyLoadingInterceptor for better testability.

Added unit tests for lazy loading of classes with custom PersistenceConstructor.
Moved integration tests for PersonRepository into its own test class.
DATAMONGO-348 - Polishing of lazy loading implementation.

Extracted DelegatingDbRefResolver and associates from MappingMongoConverter. Let MongoDbFactory expose PersistenceExceptionTranslator only to prevent invalid dependency to core package. Renamed DbRefResolveCallback to ResolverCallback. Removed AbstractDbRefResolver and moved the functionality implemented there (triggering of exception translation) into the DbRefResolver.

MappingMongoConverter now uses a slightly extended version of DbRefResolver so that we can essentially replace the MongoDbFactory dependency with the DbRefResolver one.

Added support for Objenesis based lazy-loading proxies to support domain classes without a default constructor. Explicitly check for Spring 4 being present as with it the default ProxyFactory already supports that out of the box.

Added missing JavaDoc and assertions. A lot of cleanups and removal of deprecation warnings in test cases.
DATAMONGO-348 - Added serialization support for lazy-loading for DBRefs.
DATAMONGO-793 - Adapt test cases to new initialization model of repositories.

Moved tests for nested repositories to a separate package to prevent initialization of repositories that are not meant to be instantiated actually.
DATAMONGO-791 - Added newAggregation(…) overloads to accept a List.

Aggregations can now be constructed from a list of AggregateOperations. This simplifies the usage in cases where one has to conditionally in- or exclude AggregateOperations from an AggregationPipeline.

Original pull request: #93.
DATAMONGO-789 - Support login via different authentication database.

MongoDbUtils now supports to perform the authentication against a dedicated authenticationDatabase - if no authenticationDatabase is given explicitly then the given regular database will be used. The authentication database can be configured via the authentication-dbname attribute of the db-factory element in xml config or by overriding the getAuthenticationDatabaseName() method of AbstractMongoConfiguration.

Original pull request: #92.
DATAMONGO-795 - More predictable behavior in CustomConversions.

The target type lookup previously was unpredictable in cases two converters were registered for the same source type. We now use LinkedHashMaps to register the converters and also make sure that we prefer manually registered converters over the default ones.

Related pull request: #96.
DATAMONGO-348 - Improved interceptor for lazy-loaded DBRefs.

We're now routing calls to methods declared on Object into the proxy to not accidentally resolve the lazy loading proxy on access of methods like toString() etc.
DATAMONGO-792 - Add support to configure auditing via JavaConfig.

Introduces the necessary infrastructure in form of MongoAuditingRegistrar to configure auditing with MongoDB via Annotation config. The MongoDB auditing feature can be enabled by annotating a configuration class with the EnableMongoAuditing annotation. Added section to reference documentation.

Original pull request: #94.
DATAMONGO-792 - Polishing of JavaConfig support for auditing.

Original pull request: #94.
DATAMONGO-800 - Improved AuditingIntegrationTests.

Added a tiny Thread.sleep(…) to make sure the assertion works on fast machines. If the operations after the first step all happen within a millisecond, it will fail.
DATAMONGO-801 - Prepare release 1.4.0 M1.

Updated project metadata and bumped versions.
DATAMONGO-799 - Release version 1.4.0.M1.
DATAMONGO-799 - Prepare next development iteration.