added default values for api ref metadata (#1300)

* added default values for api ref metadata

* fixing path

* changing to an alias

Author: mairaw

docfx.json

@@ -78,8 +78,22 @@
       "_displayLangs": ["csharp"],
       "author": "dotnet-bot"
     },
+    "fileMetadata": {
+      "ms.prod":
+      {
+        "api_ref/**.yml": ".net"
+      },
+      "ms.topic":
+      {
+        "api_ref/**.yml": "managed-reference"
+      },
+      "ms.author":
+      {
+        "api_ref/**.yml": "dotnetcontent"
+      }
+    },
     "dest": "_site",
     "template": [ "docs.html" ],
     "xref": ["_zip/msdn.4.5.2.zip", "_zip/namespaces.4.5.2.zip", "_zip/vs.110.zip", "_zip/vs.140.zip", "_zip/office15.zip", "_zip/missingapi.yml"]
   }
-}
+}