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.report.data.adapter/src/org/eclipse/birt/report/data/adapter/api/DataAdapterUtil.java
{
		private ILinkedResult it;
		private IResultIterator currentIterator;
		
		JSResultIteratorObject( ILinkedResult it )
		{
			this.it = it;
			if ( it.getCurrentResultType( ) == ILinkedResult.TYPE_TABLE )
				this.currentIterator = ( IResultIterator ) it.getCurrentResult( );
		}
		public String getClassName( )