Making LazyModel work when created from a class, then bound to a non-IObjectClassAwareModel.

I made LazyModel hold a reference to the original target class, then pass it to any Evaluation and bound LazyModel objects it creates. That way, it works even if it is bound to a plain IModel.

I don't know if it fits the quality requirements for wicketstuff, but let me know if any additional change is needed.