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
{
		assert invalidAggrMsg != null;
		if ( getAggrInfo( index ).getAggregation( ).getType( ) == IAggregation.RUNNING_AGGR
				|| endingGroupLevel <= getAggrInfo( index ).getGroupLevel( ) )
			currentRoundAggrValue[index].add( invalidAggrMsg.get( new Integer( index ) ) );
	}
	
	/**
	 * Calculate the value by row
	 * 
	 * @param aggrIndex
	 * @param startingGroupLevel
	 * @param endingGroupLevel
	 * @param context
	 * @param scope
	 * @throws DataException
	 */
	private boolean onRow( int aggrIndex, int startingGroupLevel,
			int endingGroupLevel, boolean populateValue )
			throws DataException
	{
		IAggrInfo aggrInfo = getAggrInfo( aggrIndex );
		Accumulator acc = null;
		boolean newGroup = false;
		boolean[] argDefs = aggrInfo.getAggregation( ).getParameterDefn( );
		if (startingGroupLevel <= aggrInfo.getGroupLevel( )) 
		{
			
			
			acc = accumulatorManagers[aggrIndex].next( );