Removed the sender parameter from DispatcherHelper.InvokeAsync (not needed anymore)
ViewModelBase.RaisePropertyChanged<T>(string, T, T, bool) throws a proper exception when first parameter (string) is null
ViewModelBase.Set now returns bool instead of void (same as ObservableObject.Set)
ViewModelBase.Set now raises PropertyChanging before the value is set
Remove old Win8 #if directives
Updated versions for 4.0.23