DATAJPA-574 - Implementation of QueryDslPredicateExecutor now considers lock mode and query hints.

The Querydsl query creation now also leverages the CrudMethodMetadata instance held in SimpleJpaRepository to apply lock mode settings and query hints to the query to be executed.
DATAJPA-576 - Improvements in JpaMappingContext setup in configuration.

Refactored JpaMappingContext to be able to work with multiple instances of Metamodel. This removes the need to wire a dedicated one in JpaMetamodelContextFactoryBean and thus makes it independent of a particular EntityManager(Factory). This significantly eases the implementation of the configuration integration.