LoadRegisteredServicesFrom extension method to respect Windsor practices

Adds capability to pull back handlers which were specifically registered as implementations of the given service.

The other LoadFrom() method brute forces all Types in Windsor which implement IConsumer or ISaga. Since Windsor provides robust capability to register any additional service types, loading only those types who have been registered as IConsumers and ISagas is the better way in the Windsor world to handle this scenario.

This is being introduced as a new extension method because changing LoadFrom() would introduce a substantial breaking change.

Commit includes:
- New LoadRegisteredServicesFrom() extension method
- Minor refactor of the WindsorContainerExtensions class
- Unit tests to capture the different scenarios the new method allows