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/__admin/mappings/array.json

@@ -0,0 +1,46 @@
+[
+  {
+    "Title": "1",
+    "Request": {
+      "Path": {
+        "Matchers": [
+          {
+            "Name": "WildcardMatcher",
+            "Pattern": "/mappings_static_1"
+          }
+        ]
+      },
+      "Methods": [
+        "get"
+      ]
+    },
+    "Response": {
+      "BodyAsJson": { "result": "mappings static_1" },
+      "Headers": {
+        "Content-Type": "application/json"
+      }
+    }
+  },
+  {
+    "Title": "2",
+    "Request": {
+      "Path": {
+        "Matchers": [
+          {
+            "Name": "WildcardMatcher",
+            "Pattern": "/mappings_static_2"
+          }
+        ]
+      },
+      "Methods": [
+        "get"
+      ]
+    },
+    "Response": {
+      "BodyAsJson": { "result": "mappings static_2" },
+      "Headers": {
+        "Content-Type": "application/json"
+      }
+    }
+  }
+]