Bug 182895 Support sort on Level attribute.
Currently in OLAP engine we only support sort on level key value. We should go ahead to support sort on level attribute value.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/olap/data/api/CubeQueryExecutorHelper.java
int count = 0;
		for ( int i = 0; i < dimPosition.length; i++ )
		{
			if ( dimPosition[i] != null )
			{
				count++;
			}
		}
		IDimension[] dimensions = cube.getDimesions( );
		String[] validDimensionName = new String[count];
		IDiskArray[] validDimPosition = new IDiskArray[count];
		int pos = 0;
		for ( int i = 0; i < dimPosition.length; i++ )
		{
			if ( dimPosition[i] != null )
			{
				validDimPosition[pos] = dimPosition[i];
				validDimensionName[pos] = dimensions[i].getName( );
				pos++;
			}
		}
		FactTableRowIterator facttableRowIterator = new FactTableRowIterator( cube.getFactTable( ),
				validDimensionName,
				validDimPosition,
				computedMeasureHelper,
				stopSign );
		DimensionResultIterator[] dimensionResultIterator = populateDimensionResultIterator( dimPosition, stopSign );
		AggregationExecutor aggregationCalculatorExecutor = new AggregationExecutor( dimensionResultIterator,
				facttableRowIterator,
				aggregations );