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.tests/test/org/eclipse/birt/data/engine/olap/api/CubeFeaturesTest.java
binding4.setExpression( new ScriptExpression("dimension[\"dimension2\"][\"level21\"]") );
		cqd.addBinding( binding4 );
		
		IBinding binding5 = new Binding( "measure1" );
		binding5.setExpression( new ScriptExpression("measure[\"measure1\"]") );
		cqd.addBinding( binding5 );
		
		CubeSortDefinition sorter = new CubeSortDefinition();
		sorter.setExpression( "dimension[\"dimension2\"][\"level21\"]" );
		sorter.setSortDirection( ISortDefinition.SORT_DESC );
		sorter.setTargetLevel( level21 );
		cqd.addSort( sorter );
		DataEngine engine = DataEngine.newDataEngine( DataEngineContext.newInstance( DataEngineContext.DIRECT_PRESENTATION,
				null,
				null,
				null ) );
		this.createCube( engine );
		
		cqd.setCacheQueryResults( true );
		
		IPreparedCubeQuery pcq = engine.prepare( cqd, null );
		ICubeQueryResults queryResults = pcq.execute( null );
		CubeCursor cursor = queryResults.getCubeCursor( );
		List columnEdgeBindingNames = new ArrayList();
		columnEdgeBindingNames.add( "edge1level1" );
		columnEdgeBindingNames.add( "edge1level2" );
		
		
		cqd.setQueryResultsID( queryResults.getID( ) );
		pcq = engine.prepare( cqd, null );