Add ResultIterator::next() and ResultIterator::delete()

Here is the sample code to get recognized result/confidence word by word.
```
boolean AddFromTessApi( TessBaseAPI tessApi)
    {
        ResultIterator rit = tessApi.getResultIterator();
        if (rit==null) {
            Log.e(TAG, "RIterator is null");
            return false;
        }
        int level = TessBaseAPI.PageIteratorLevel.RIL_WORD;
        do {
            AddOneRecord(rit.getUTF8Text(level),
                    rit.confidence(level));
        }while (rit.next(level));
        rit.delete();
        return true;
    }
```