Bug 141959 Changing data set didn't clean old column bindings
Steps to reproduce: 1.Add two data sets, "ds1" and "ds2" 2.Add a table, binding with "ds1". All "ds1" column bindings generate automatically, that's good 3.Change "ds1" to None Expected result: All "ds1" column bindings should be cleaned Actual result: All "ds1" column bindings are still there. If changing to "ds2", "ds2" column bindings will be added after them.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ColumnBindingDialog.java
public Object[] getElements( Object inputElement )
		{
			List elementsList = getBindingList( (DesignElementHandle) inputElement );
			elementsList.add( dummyChoice );
			return elementsList.toArray( );
		}
	};
	private ITableLabelProvider labelProvider = new ITableLabelProvider( ) {
		public Image getColumnImage( Object element, int columnIndex )
		{
			return null;
		}
		public String getColumnText( Object element, int columnIndex )
		{
			if ( element == dummyChoice )
			{
				if ( columnIndex == 1 )
				{
					return INPUT_PROPMT;
				}
				return ""; 
			}
			ComputedColumnHandle handle = ( (ComputedColumnHandle) element );
			String text = null;
			switch ( columnIndex )
			{
				case 1 :
					text = handle.getName( );
					break;
				case 2 :