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
if( startingGroupLevel > aggrInfo.getCalcualteLevel() )
				accepted = false;
		}
		
		if ( accepted )
		{
			
			
			assert argDefs.length == aggrArgs[aggrIndex].length;
			try
			{
				if ( aggrInfo.getArgument( ).length > argDefs.length )
					throw new DataException( "Invalid aggregation definition");
				for ( int i = 0; i < argDefs.length; i++ )
				{
					
					
					
					
					if ( argDefs[i] || newGroup )
					{
						IBaseExpression argExpr = aggrInfo.getArgument( )[i];
						try
						{
							aggrArgs[aggrIndex][i] = ExprEvaluateUtil.evaluateValue( argExpr,
									this.populator.getCache( ).getCurrentIndex( ),
									this.populator.getCache( ).getCurrentResult( ),
									this.populator.getQuery( ).getExprProcessor( ).getScope( ) );
						}
						catch ( BirtException e )