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
public EdgeInfoGenerator getEdgeInfo( )
	{
		return this.edgeInfo;
	}
	/**
	 * 
	 * @return
	 */
	public IAggregationResultSet getAssociationQueryResultSet( )
	{
		return this.rs;
	}
	/**
	 * Get dimension's metadata
	 * @return
	 */
	public RowDataMetaData getRowDataMetaData( )
	{
		return new RowDataMetaDataImpl( metaData );
	}
	/**
	 * Move cursor to the next row.Return false if the next row does not exist.
	 * 
	 * @return
	 * @throws OLAPException
	 */
	public boolean next( ) throws OLAPException
	{
		return this.edgeInfo.dim_next( dimAxisIndex );
	}