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
try
		{
			return aggregationCalculatorExecutor.execute( stopSign );
		}
		finally
		{
			facttableRowIterator.close( );
		}
	}
	
	/**
	 * 
	 * @param resultLevels
	 * @param position
	 * @param stopSign
	 * @return
	 * @throws DataException
	 * @throws IOException
	 */
	private DimensionResultIterator[] populateDimensionResultIterator( IDiskArray[] position, StopSign stopSign ) throws DataException, IOException
	{
		IDimension[] dimensions = cube.getDimesions( );
		DimensionResultIterator[] dimResultSet = new DimensionResultIterator[dimensions.length];
		int count = 0;
		for ( int i = 0; i < dimensions.length; i++ )
		{
			if ( position[i] == null )
				{
					dimResultSet[i] = new DimensionResultIterator( (Dimension) dimensions[i],
							dimensions[i].findAll( ), stopSign);