Bug 132805 Set descending to outer group will affect inner group.
Description: Set descending to outer group will affect inner group. Steps to reproduce: 1. New a sample datasource and dataset from orders. 2. Drag the dataset to Layout. 3. Add a group on ordernumber, interval 10, descending. 4. Add another group on orderdate, interval day 2, ascending. 5. Preview. Expected result: Data are grouped correctly. Actual result: Inner group didn't work unless you set outer group's sort to asc.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
* Prepare Executor so that it is ready to execute the query
	 * 
	 * @param outerRts
	 * @param targetScope
	 * @throws DataException
	 */
	void prepareExecution( IQueryResults outerRts, Scriptable targetScope ) throws DataException
	{
		if(isPrepared)return;
		
		this.parentScope = targetScope;
		dataSource = findDataSource( );
		if ( outerRts != null )
		{
			outerResults = ( (IQueryService) outerRts );
			if ( outerResults.isClosed( ) )
			{
				
				throw new DataException( ResourceConstants.RESULT_CLOSED );
			}
			this.nestedLevel = outerResults.getNestedLevel( );
			this.setParentExecutorHelper(outerResults.getExecutorHelper( ));
		}
		
		
		
		
		dataSet = newDataSetRuntime();
		assert dataSet != null;