IncrementalResult Implemented

Still needs some more tests to test the asynchronous operation. At least for synchronous operation I think it works now.

I had to modify the API a bit, because stuff like "getResultCount" doesn't really make sense given the asynchronous nature of the class's operation. As soon as you got back the result from it it could have already been invalidated by the producer thread adding new results.
We should agree on a standard for inner class placement. I've been putting mine at the end of the class, but the Oracle coding standards don't say anything about it so we should make a decision.