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
private List rowSort = null;
	private List columnSort = null;
	
	private boolean isBreakHierarchy = true;
	
	private IComputedMeasureHelper computedMeasureHelper = null;
	
	private Map dimLevelsMap = null;
	private List aggrFilterHelpers;
	
	private static Logger logger = Logger.getLogger( CubeQueryExecutorHelper.class.getName( ) );
	
	/**
	 * 
	 * @param cube
	 */
	public CubeQueryExecutorHelper( ICube cube ) throws DataException
	{
		this(cube, null);
	}
	
	/**
	 * 
	 * @param cube
	 */
	public CubeQueryExecutorHelper( ICube cube, IComputedMeasureHelper computedMeasureHelper ) throws DataException
	{
		Object[] params = {cube, computedMeasureHelper};
		logger.entering( CubeQueryExecutorHelper.class.getName( ),
				"CubeQueryExecutorHelper",