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
* 
	 * @param aggrTable
	 * @param odiResult
	 * @throws DataException 
	 */
	public AggregationHelper( IAggrDefnManager manager, ResultSetPopulator populator ) throws DataException
	{
		this.populator = populator;
		this.manager = manager;
		this.currentRoundAggrValue = new List[0];
		this.populateAggregations( );
	}
	private void populateAggregations( ) throws DataException
	{
		
			this.currentAggrCount = manager.getAggrCount( );
			if ( currentAggrCount > 0 )
			{
				currentRoundAggrValue = new List[currentAggrCount];
				aggrArgs = new Object[currentAggrCount][];
				for ( int i = 0; i < this.currentAggrCount; i++ )
				{
					currentRoundAggrValue[i] = new BasicCachedList( );
					IAggrInfo aggrInfo = this.manager.getAggrDefn( i );
					
					aggrArgs[i] = new Object[aggrInfo.getAggregation( )
							.getParameterDefn( ).length];
				}
				accumulatorManagers = new AccumulatorManager[currentAggrCount];
			}