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
/*******************************************************************************
 * Copyright (c) 2004, 2005 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/
package org.eclipse.birt.data.engine.olap.data.impl.aggregation.sort;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import org.eclipse.birt.data.engine.core.DataException;
import org.eclipse.birt.data.engine.olap.data.api.DimLevel;
import org.eclipse.birt.data.engine.olap.data.api.IAggregationResultRow;
import org.eclipse.birt.data.engine.olap.data.api.IAggregationResultSet;
import org.eclipse.birt.data.engine.olap.data.impl.aggregation.AggregationResultRow;
import org.eclipse.birt.data.engine.olap.data.impl.aggregation.AggregationResultSet;
import org.eclipse.birt.data.engine.olap.data.impl.dimension.Member;
import org.eclipse.birt.data.engine.olap.data.util.BufferedStructureArray;
import org.eclipse.birt.data.engine.olap.data.util.CompareUtil;
import org.eclipse.birt.data.engine.olap.data.util.IDiskArray;