Added OrderCloseByRequest. Changed functions OrderCloseBy to use request pattern

MtApi/Requests/OrderCloseByRequest.cs

@@ -0,0 +1,15 @@
+namespace MtApi.Requests
+{
+    public class OrderCloseByRequest: RequestBase
+    {
+        public int Ticket { get; set; }
+        public int Opposite { get; set; }
+
+        public int? ArrowColor { get; set; }
+
+        public override RequestType RequestType
+        {
+            get { return RequestType.OrderCloseBy; }
+        }
+    }
+}

MtApi/Requests/RequestType.cs

@@ -7,5 +7,6 @@
         GetOrders       = 2,
         OrderSend       = 3,
         OrderClose      = 4,
+        OrderCloseBy    = 5
     }
 }