add GroupFilter property for UI drop down etc to show the active/applied filter

#64

DataCenter_Windows/WindowsDataCenter/Interfaces/UserList.cs

@@ -23,7 +23,7 @@ namespace Interfaces
                 return (TotalUserCount / PageSize);
             }
         }
-
+        public Group GroupFilter { get; set; }
         public int PageSize { get; set; }
         public int PageNumber { get; set; }
     }