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/impl/ComputedColumnHelper.java
{
	private ComputedColumnHelperInstance dataSetInstance;
	private ComputedColumnHelperInstance resultSetInstance;
	private ComputedColumnHelperInstance availableModeInstance;
	private int currentModel;
	private List allCC;
	private static Logger logger = Logger.getLogger( ComputedColumnHelper.class.getName( ) );
	
	/**
	 * 
	 * @param dataSet
	 * @param dataSetCCList
	 * @param resultSetCCList
	 * @throws  
	 */
	ComputedColumnHelper( DataSetRuntime dataSet, List dataSetCCList,
			List resultSetCCList ) throws DataException
	{
		Object[] params = { dataSet, dataSetCCList, resultSetCCList };
		logger.entering( ComputedColumnHelper.class.getName( ),
				"ComputedColumnHelper",
				params );
		
		this.dataSetInstance = new ComputedColumnHelperInstance( dataSet,
				dataSetCCList );
		this.resultSetInstance = new ComputedColumnHelperInstance( dataSet,