public HandlerRegistration addColumnSortHandler(ColumnSortEvent.Handler handler) {
        return addHandler(handler, ColumnSortEvent.getType());
    }
Add a handler to handle {@link ColumnSortEvent}s.

@param handler the {@link ColumnSortEvent.Handler} to add
@return a {@link HandlerRegistration} to remove the handler
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/AbstractCellTable.java