code: public void setSorting(List<SortProperty> newSorting) {
  		Validate.notNull(newSorting, "Sorting required");
  
  		if (!sorting.equals(newSorting)) {
  			sorting.clear();
  			sorting.addAll(newSorting);
  			selectionIndex = -1;
  			clearCache();
  		}
  	}
docs: Sets sorting, does nothing if sorting will not change. Clears the cache
  but does not notify observers for data changes.
  
  @param newSorting
  List of SortProperties, replacing