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/impl/aggregation/sort/AggregationSortHelper.java
SortKey[] aggr ) throws IOException,
			DataException
	{
		for ( int i = 0; i < aggr.length; i++ )
		{
			IAggregationResultSet rSet = aggr[i].getTargetResultSet( );
			filterResultSet( rSet, aggr[i] );
		}
	}
	private static void filterResultSet( IAggregationResultSet rSet,
			SortKey key ) throws IOException, DataException
	{
		IDiskArray[] diskArray = new IDiskArray[key.getAxisQualifiers( ).length];
		AggregationResultRowNavigator[] result = new AggregationResultRowNavigator[key.getAxisQualifiers( ).length];
		for ( int i = 0; i < diskArray.length; i++ )
		{
			diskArray[i] = new BufferedStructureArray( AggregationResultRow.getCreator( ),
					4096 );
		}
		for ( int j = 0; j < rSet.length( ); j++ )
		{
			rSet.seek( j );
			int[] index = key.getAxisQualifiers( )[0].getLevelIndex( );
			Object[] values = new Object[index.length];
			for ( int i = 0; i < index.length; i++ )
			{
				values[i] = rSet.getLevelKeyValue( index[i] )[0];
			}
			for ( int i = 0; i < key.getAxisQualifiers( ).length; i++ )
			{