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

examples/WireMock.Net.Console.NETCoreApp2/__admin/mappings/BodyAsFileExample.json

@@ -0,0 +1,22 @@
+{
+    "Request": {
+        "Path": {
+            "Matchers": [
+                {
+                    "Name": "WildcardMatcher",
+                    "Pattern": "/bodyasfilexmltest",
+                    "IgnoreCase": false
+                }
+            ]
+        },
+        "Methods": [
+            "get"
+        ]
+    },
+    "Response": {
+        "StatusCode": 200,
+        "Headers": {"Content-Type": "application/xml"},
+        "BodyAsFile": "MyXmlResponse.xml",
+        "UseTransformer": false
+    }
+}