model+ndn.cxx+test: Finishing implementation of ApiFace (now timeouts are working as well)

Also, adding a basic test case to test ApiFace

Refs #1005 (http://redmine.named-data.net/)
diff --git a/ndn.cxx/ndn-api-face.h b/ndn.cxx/ndn-api-face.h
index 8c589bb..160540e 100644
--- a/ndn.cxx/ndn-api-face.h
+++ b/ndn.cxx/ndn-api-face.h
@@ -56,6 +56,12 @@
   ~ApiFace ();
 
   /**
+   * @brief Shutdown the API face
+   */
+  void
+  Shutdown ();
+  
+  /**
    * @brief Express Interest
    *
    * @param name the Interest name