NFD+model+apps+helper+tests: Upgrade NFD and related changes

Based on NFD:commit:2fc649bfc67b93b4191cfbee5bcd70330bfb48f0 (version 0.3.4)

Change-Id: I89f5182600467171797af4f8f83e1edffe14ad95
Refs: #3125
diff --git a/model/ndn-app-face.hpp b/model/ndn-app-face.hpp
index 5ae6593..ab3de90 100644
--- a/model/ndn-app-face.hpp
+++ b/model/ndn-app-face.hpp
@@ -55,20 +55,28 @@
 public: // from nfd::Face
   /**
    * @brief Send Interest towards application
-   *
-   * @note To send Interest from application, use `AppFace::onReceiveInterest(interest)`
    */
   virtual void
   sendInterest(const Interest& interest);
 
   /**
    * @brief Send Data towards application
-   *
-   * @note To send Data from application, use `AppFace::onReceiveData(data)`
    */
   virtual void
   sendData(const Data& data);
 
+  /**
+   * @brief Send Interest towards NFD
+   */
+  void
+  onReceiveInterest(const Interest& interest);
+
+  /**
+   * @brief Send Data towards NFD
+   */
+  void
+  onReceiveData(const Data& data);
+
   virtual void
   close();