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
int endingGroupLevel = this.getEndingGroupLevel( );
			for ( int i = 0; i < validAggregationArray.length; i++ )
			{
				int index = validAggregationArray[i];
				if ( invalidAggrSet != null
						&& invalidAggrSet.contains( new Integer( index ) ) )
				{
					addInvalidAggrMsg( index, endingGroupLevel );
					continue;
				}
				if ( onRow( index,
						startingGroupLevel,
						endingGroupLevel,
						populateAggrValue[index] ) == false )
				{
					addInvalidAggrMsg( index, endingGroupLevel );
					if ( invalidAggrSet == null )
						invalidAggrSet = new HashSet( );
					invalidAggrSet.add( new Integer( index ) );
				}
			}
		} while ( this.populator.getResultIterator( ).next( ) );
	}
	/**
	 * 
	 * @param index
	 * @param endingGroupLevel
	 * @throws DataException 
	 */
	private void addInvalidAggrMsg( int index, int endingGroupLevel ) throws DataException