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/impl/ComputedColumnHelper.java
{
	private DataSetRuntime dataSet;
	
	private List ccList;
	
	private IComputedColumn[] computedColumn;
	
	private int[] columnIndexArray;
	
	private boolean isPrepared;
	protected static Logger logger = Logger.getLogger( ComputedColumnHelper.class.getName( ) );
	public ComputedColumnHelperInstance( DataSetRuntime dataSet,
			List computedColumns )
	{
		
		
		this.ccList = new ArrayList( );
		for ( int i = 0; i < computedColumns.size( ); i++ )
			this.ccList.add( computedColumns.get( i ) );
		this.isPrepared = false;
		this.dataSet = dataSet;
	}
	public List getComputedColumnList( )
	{
		return this.ccList;
	}