Aspect for setting the correct class loader when invoking a method in the service layer.
When invoking a method from a bundle in the service layer of another bundle the classloader of the invoking bundle is used. This poses the problem that the invoking class loader needs to know about
classes in the service layer of the other bundle. This aspect sets the ContextClassLoader of the invoking thread to that of the other bundle, the bundle that owns the method in the service
layer which is being invoked. After the invoke is completed the aspect sets the ContextClassLoader back to the original classloader of the invoker.