support a way to re-sort a ListModel under MVVM pattern

Use case

• a listbox is sorted by sort="auto(language)" by clicking a listheader
• After adding a new item into ListModel, how to force ListModel to sort again?

Current Result

1. call Listheader.sort() , but this is not MVVM way
2. ListModelList.sort(Comparator<E> cmpr, final boolean ascending) requires 2 parameters but app developers can't get the existing comparator and sorting order

Proposed solution

Check attached SortedListModelList
1. a sort() method that sorts the ListModel with the previous comparator and sorting order
2. in add(), insert the newly-add item into the proper position instead of sorting the whole list after insertion to keep the whole list sorted in the same way.