Fixed Issue MAGN4944

Issue: http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4944
Addded 1 in-port to nodes from DSVarArgFunction
@Steell  Please review it. Thanks
@Steell Yes, that's why I used ```var argName = arg.Name.Remove(arg.Name.Length - 1) + idx.ToString();``` idx.ToString() will return the index of this parameter. For example, for String.Join, the 1st parameter is "separator" then when we add 1 more parameter, it will be string1,behaving as it is now.