Bug 27491 Cannot add classpath variable to project
build id : 200212020010 The buttons OK and extend... are always disabled in the add variable dialog
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/dialogfields/ListDialogField.java
fRemoveButtonIndex= removeButtonIndex;
	}
	/**
	 * Sets the index of the 'up' button in the button label array passed in the constructor.
	 * The behaviour of the button marked as the 'up' button will then be handled internally.
	 * (enable state, button invocation behaviour)
	 */	
	public void setUpButtonIndex(int upButtonIndex) {
		Assert.isTrue(upButtonIndex < fButtonLabels.length);
		fUpButtonIndex= upButtonIndex;
	}
	/**
	 * Sets the index of the 'down' button in the button label array passed in the constructor.
	 * The behaviour of the button marked as the 'down' button will then be handled internally.
	 * (enable state, button invocation behaviour)
	 */	
	public void setDownButtonIndex(int downButtonIndex) {
		Assert.isTrue(downButtonIndex < fButtonLabels.length);
		fDownButtonIndex= downButtonIndex;
	}
	
	/**
	 * Sets the viewerSorter.
	 * @param viewerSorter The viewerSorter to set
	 */
	public void setViewerSorter(ViewerSorter viewerSorter) {
		fViewerSorter= viewerSorter;
	}
	
	public void setTableColumns(ColumnsDescription column) {