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
* @return
	 */
	public List getComputedColumnList( )
	{
		if ( this.getCurrentInstance( ) != null )
			return this.getCurrentInstance( ).getComputedColumnList( );
		else
			return this.allCC;
	}
	/**
	 * 
	 * @param rePrepare
	 */
	public void setRePrepare( boolean rePrepare )
	{
		if ( this.getCurrentInstance( ) != null )
			this.getCurrentInstance( ).setRePrepare( rePrepare );
	}
	/**
	 * 
	 * @param model
	 */
	public void setModel( int model )
	{
		this.currentModel = model;
	}
		
	/**
	 * 
	 * @param dataSetCCList