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/driver/DimensionAxis.java
{
	private IResultSetMetaData metaData;
	private IAggregationResultSet rs;
	private int dimAxisIndex, levelIndex, attrIndex;
	private EdgeInfoGenerator edgeInfo;
	private boolean isMirrored = false; 
	private int aggrSortType = IDimensionSortDefn.SORT_UNDEFINED;
	private Vector valueObjects = null;
	/**
	 * 
	 * @param container
	 * @param rs
	 * @param dimAixsIndex
	 * @param levelIndex
	 * @param attrIndex
	 */
	public DimensionAxis( EdgeAxis container, IAggregationResultSet rs,
			int dimAixsIndex, int levelIndex, int attrIndex )