Bug 189706 Enhance computed column aggregation function handling in UI.
Due to the issue discussed in 189705, current computed column aggregation builder in data set editor has bugs to extend: 1.When new a computed column, the aggregation argument field cannot be correctly set. 2.The argument field cannot be correct grayed out when user select a aggregation function without arguments 3.The available aggregation function list is incomprehensive 4.Some aggregation function cannot be set to model(say, weightedAve).
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/executor/aggregation/AggregationHelper.java
*
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/
package org.eclipse.birt.data.engine.executor.aggregation;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.eclipse.birt.core.data.DataTypeUtil;
import org.eclipse.birt.core.exception.BirtException;
import org.eclipse.birt.data.engine.api.IBaseExpression;
import org.eclipse.birt.data.engine.api.aggregation.Accumulator;
import org.eclipse.birt.data.engine.api.aggregation.Aggregation;
import org.eclipse.birt.data.engine.api.aggregation.IAggregation;
import org.eclipse.birt.data.engine.api.aggregation.IBuildInAggregation;
import org.eclipse.birt.data.engine.cache.BasicCachedList;
import org.eclipse.birt.data.engine.core.DataException;
import org.eclipse.birt.data.engine.executor.transform.ResultSetPopulator;
import org.eclipse.birt.data.engine.expression.ExprEvaluateUtil;
import org.eclipse.birt.data.engine.odi.IAggrInfo;
import org.eclipse.birt.data.engine.odi.IAggrDefnManager;
import org.eclipse.birt.data.engine.odi.IAggrValueHolder;
import org.eclipse.birt.data.engine.odi.IResultObject;
/**
 * 
 */
public class AggregationHelper implements IAggrValueHolder