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
| SWT.FULL_SELECTION
				| SWT.BORDER
				| ( canSelect ? SWT.CHECK : 0 ) );
		GridData gd = new GridData( GridData.FILL_BOTH );
		gd.heightHint = 200;
		table.setLayoutData( gd );
		table.setLinesVisible( true );
		table.setHeaderVisible( true );
		table.addKeyListener( new KeyAdapter( ) {
			/**
			 * @see org.eclipse.swt.events.KeyAdapter#keyReleased(org.eclipse.swt.events.KeyEvent)
			 */
			public void keyReleased( KeyEvent e )
			{
				
				if ( e.keyCode == SWT.DEL )
				{
					IStructuredSelection selection = (IStructuredSelection) bindingTable.getSelection( );
					if ( selection.getFirstElement( ) instanceof ComputedColumnHandle )
					{
						deleteRow( (ComputedColumnHandle) selection.getFirstElement( ) );
					}
				}
			}
		} );
		String[] columns = null;
		int[] columnWidth = null;
		CellEditor[] cellEditors;
		expressionCellEditor = new ExpressionCellEditor( table );
		columns = new String[]{