Merge into the stef_negate_matcher branch (solves issue #133) (#135)

* Fixed #133

* tests: add parametrised tests that cover various body matchers for json

* Code review comments (BodyAsStringOriginal)

* tests: minor method name change

src/WireMock.Net/Util/BodyData.cs

@@ -13,7 +13,7 @@ namespace WireMock.Util
         public Encoding Encoding { get; set; }
 
         /// <summary>
-        /// The body as string.
+        /// The body as string, this is defined when BodyAsString or BodyAsJson are not null.
         /// </summary>
         public string BodyAsString { get; set; }