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/query/view/QueryExecutor.java
AggregationDefinition[] aggregations;
		if ( columnEdgeDefn == null && rowEdgeDefn == null )
			aggregations = new AggregationDefinition[aggregationCount];
		else if ( columnEdgeDefn == null || rowEdgeDefn == null )
			aggregations = new AggregationDefinition[aggregationCount + 1];
		else
			aggregations = new AggregationDefinition[aggregationCount + 2];
		int aggrIndex = 0;
		int[] sortType;
		if ( columnEdgeDefn != null )
		{
			DimLevel[] levelsForFilter = new DimLevel[levelsOnColumn.length];
			sortType = new int[levelsOnColumn.length];
			for ( int i = 0; i < levelsOnColumn.length; i++ )
			{
				levelsForFilter[i] = new DimLevel( levelsOnColumn[i] );
				sortType[i] = getSortDirection( levelsForFilter[i], query );
			}
			aggregations[aggrIndex] = new AggregationDefinition( levelsForFilter,
					sortType,
					null );
			aggrIndex++;
		}
		if ( rowEdgeDefn != null )
		{
			DimLevel[] levelsForFilter = new DimLevel[levelsOnRow.length];
			sortType = new int[levelsOnRow.length];
			for ( int i = 0; i < levelsOnRow.length; i++ )
			{
				levelsForFilter[i] = new DimLevel( levelsOnRow[i] );