SPARQLStore / QE / Count query results

Count query results are returned as an integer which makes it impossible to return a proper object or for that matter possible errors

- Add `SMWQueryResult::setCountValue`, `SMWQueryResult::getCountValue`
- `SMWQueryProcessor` is modified in away that it detects an integer or object and acts accordingly

```
$queryResult->setCountValue( $resultWrapper->getNumericValue() );
```

Relates to #375