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/transform/pass/DataSetProcessUtil.java
exprs = new IBaseExpression[args.size( ) + 1];
					offset = 1;
					exprs[0] = cc.getExpression( );
				}
				else
					exprs = new IBaseExpression[args.size( )];
				for ( int j = offset; j < args.size( )+offset; j++ )
				{
					exprs[j] = (IBaseExpression) args.get( j - offset );
				}
				for ( int j = 0; j < exprs.length; j++ )
				{
					compiler.compile( exprs[j], cx );
				}
				if ( cc.getAggregateFilter( )!= null )
					compiler.compile( cc.getAggregateFilter( ), cx );
				IAggregation aggrFunction = AggregationFactory.getInstance( )
						.getAggregation( cc.getAggregateFunction( ) );
				IAggrInfo aggrInfo = new AggrInfo( cc.getName( ),
						0,
						aggrFunction,
						exprs,
						cc.getAggregateFilter( ) );
				aggrInfos.add( aggrInfo );
				aggrNames.add( cc.getName( ) );
			}
			
			if ( !psController.needDoOperation( PassStatusController.DATA_SET_FILTERING ) )
				PassUtil.pass( populator,
						new OdiResultSetWrapper( populator.getResultIterator( ) ),