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
this.populator.getQuery( ).setMaxRows( originalMaxRows );
	}
	
	/**
	 * 
	 * @param aggrComputedColumns
	 * @throws DataException
	 */
	private void populateAggrCCs( List aggrComputedColumns )
			throws DataException
	{
		if ( aggrComputedColumns.size( ) == 0 )
			return;
		ExpressionCompiler compiler = new ExpressionCompiler( );
		compiler.setDataSetMode( true );
		try
		{
			Context cx = Context.enter( );
			List aggrInfos = new ArrayList( );
			List aggrNames = new ArrayList( );
			for ( int i = 0; i < aggrComputedColumns.size( ); i++ )
			{
				ComputedColumn cc = (ComputedColumn) aggrComputedColumns.get( i );
				List args = cc.getAggregateArgument( );
				IBaseExpression[] exprs = null;
				int offset = 0;
				if ( cc.getExpression( ) != null )
				{