Fix BodyAsFile to also allow relative paths (#244)

* Read only .json files as static mapping files and fix current folder for BodyAsFile

* include .json again

* LocalFileSystemHandler_ReadResponseBodyAsFile_Throws

* Read array from static mappings folder

* xml soap example

test/WireMock.Net.Tests/Handlers/LocalFileSystemHandlerTests.cs

@@ -33,5 +33,12 @@ namespace WireMock.Net.Tests.Handlers
             // Act
             Check.ThatCode(() => _sut.WriteMappingFile(null, null)).Throws<ArgumentNullException>();
         }
+
+        [Fact]
+        public void LocalFileSystemHandler_ReadResponseBodyAsFile_Throws()
+        {
+            // Act
+            Check.ThatCode(() => _sut.ReadResponseBodyAsFile(null)).Throws<ArgumentNullException>();
+        }
     }
 }