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
{
		this.parentHelper = helper;
	}
	
	/**
	 * 
	 * @param cx
	 * @param dataSetFilters
	 * @param queryFilters
	 * @param temporaryComputedColumns
	 * @return
	 */
	private List prepareFilters(Context cx, List dataSetFilters, List queryFilters,
			List temporaryComputedColumns) {
		List result = new ArrayList();
		prepareFilter(cx, dataSetFilters, temporaryComputedColumns, result);
		prepareFilter(cx, queryFilters, temporaryComputedColumns, result);
		return result;
	}
	/**
	 * 
	 * @param cx
	 * @param dataSetFilters
	 * @param temporaryComputedColumns
	 * @param result
	 */
	private void prepareFilter(Context cx, List dataSetFilters, List temporaryComputedColumns, List result) {
		if (dataSetFilters != null && !dataSetFilters.isEmpty()) {
			Iterator it = dataSetFilters.iterator();
			for (int i = 0; it.hasNext(); i++) {