Modified DataManager to not incorrectly handle default view.

Done by:
- Enforcing that the LocalDataManager always hits the IncrementalResult first, rather than just assuming the NetworkDataManager will return after it.
- Fixing DataFilter so that it works correctly when no filtering is done. Before it would not accept any items if no filtering was done.

Fixed AttachmentItem local serialization. LocalDataManager did not recognize AttachmentItems when serializing locally stored data in.