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/expression/ExpressionProcessor.java
if ( aggrList == null || table == null )
		{
			return;
		}
		
		
		if ( helper.hasNestedAggregate( ) )
		{
			table.calculate( resultIterator,
					dataset.getScriptScope( ),
					(JSAggrValueObject) dataset.getJSTempAggrValueObject( ) );
		}
		else
		{
			table.calculate( resultIterator, dataset.getScriptScope( ) );
		}
		Scriptable aggrObj = table.getJSAggrValueObject( );
		dataset.setJSTempAggrValueObject( aggrObj );;
		for ( int i = 0; i < aggrList.size( ); i++ )
		{
			AggregateObject obj = (AggregateObject) aggrList.get( i );
			obj.setAvailable( true );
			if ( availableAggrList == null )
				availableAggrList = new ArrayList( );
			if ( !availableAggrList.contains( obj ) )
				availableAggrList.add( obj );
		}
	}
		
	/**