Upgraded to improved Spring Data repository configuration API.

AbstractRepositoryConfigurationSourceSupport now uses the newly
introduced RepositoryConfigurationDelegate instead of effectively
reimplementing Spring Data Commons functionality which was prone to
changes in the API (code that wasn't considered to be API in the first
place).

Switched from implementing BeanClassLoaderAware to ResourceLoaderAware
to avoid having to set up a DefaultResourceLoader which should also
improve the IDE integration.