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 );
		
		IBinding binding6 = new Binding( "rowGrandTotal");
		binding6.setExpression( new ScriptExpression("measure[\"measure1\"]") );
		binding6.setAggrFunction( IBuildInAggregation.TOTAL_SUM_FUNC );
		binding6.addAggregateOn( "dimension[\"dimension2\"][\"level21\"]" );
		cqd.addBinding( binding6 );
		
		IBinding binding7 = new Binding( "columnGrandTotal");
		binding7.setExpression( new ScriptExpression("measure[\"measure1\"]") );
		binding7.setAggrFunction( IBuildInAggregation.TOTAL_SUM_FUNC );
		binding7.addAggregateOn( "dimension[\"dimension1\"][\"level11\"]" );
		binding7.addAggregateOn( "dimension[\"dimension1\"][\"level12\"]" );
		cqd.addBinding( binding7 );
		
		IBinding binding8 = new Binding( "grandTotal");
		binding8.setExpression( new ScriptExpression("measure[\"measure1\"]") );
		binding8.setAggrFunction( IBuildInAggregation.TOTAL_SUM_FUNC );
		cqd.addBinding( binding8 );
		
		
		CubeSortDefinition sorter1 = new CubeSortDefinition();
		sorter1.setExpression( "dimension[\"dimension2\"][\"level21\"]" );
		sorter1.setSortDirection( ISortDefinition.SORT_DESC );