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/Settings/IWireMockServerSettings.cs

@@ -143,5 +143,11 @@ namespace WireMock.Settings
         /// </summary>
         /// [PublicAPI]
         bool? AllowAnyHttpStatusCodeInResponse { get; set; }
+
+        /// <summary>
+        /// Set to true to disable Json deserialization when processing requests. (default set to false).
+        /// </summary>
+        [PublicAPI]
+        bool? DisableJsonBodyParsing { get; set; }
     }
 }