Issue #89: Changed function PositionOpen to use json request/response

MtApi5/Requests/PositionOpenRequest.cs

@@ -0,0 +1,15 @@
+namespace MtApi5.Requests
+{
+    internal class PositionOpenRequest: RequestBase
+    {
+        public override RequestType RequestType => RequestType.PositionOpen;
+
+        public string Symbol { get; set; }
+        public ENUM_ORDER_TYPE OrderType { get; set; }
+        public double Volume { get; set; }
+        public double Price { get; set; }
+        public double Sl { get; set; }
+        public double Tp { get; set; }
+        public string Comment { get; set; }
+    }
+}

MtApi5/Requests/RequestType.cs

@@ -1,13 +1,13 @@
-using System.Diagnostics.CodeAnalysis;
+// ReSharper disable InconsistentNaming
 
 namespace MtApi5.Requests
 {
-    [SuppressMessage("ReSharper", "InconsistentNaming")]
     internal enum RequestType
     {
         Unknown         = 0,
         CopyTicks       = 1,
         iCustom         = 2,
-        OrderSend       = 3
+        OrderSend       = 3,
+        PositionOpen    = 4
     }
 }