Option to disable JSON deserialization (#434)

* Option to disable JSON deserialization

* Fix build errors, add test case

* make new parameter optional

* set default for contentType as well

src/WireMock.Net/Owin/WireMockMiddlewareOptions.cs

@@ -45,5 +45,8 @@ namespace WireMock.Owin
 
         /// <inheritdoc cref="IWireMockMiddlewareOptions.AllowAnyHttpStatusCodeInResponse"/>
         public bool? AllowAnyHttpStatusCodeInResponse { get; set; }
+
+        /// <inheritdoc cref="IWireMockMiddlewareOptions.DisableResponseBodyParsing"/>
+        public bool? DisableJsonBodyParsing { get; set; }
     }
 }