management: Implementing nrd::Controller and introducing new secret
environment option to enable NRD Prefix management protocol

Usage for the secret NFD and NRD environment variables

    export NFD=1
    export NRD=1
    <run app>

or

    NFD=1 NRD=1 <run app>

Change-Id: I874acbdcf7038f4d0fa05c59b34cd46d6ae627b0
diff --git a/src/face.cpp b/src/face.cpp
index bc6d877..919ea5d 100644
--- a/src/face.cpp
+++ b/src/face.cpp
@@ -17,6 +17,7 @@
 
 #include "management/ndnd-controller.hpp"
 #include "management/nfd-controller.hpp"
+#include "management/nrd-controller.hpp"
 
 namespace ndn {
 
@@ -62,7 +63,12 @@
   m_processEventsTimeoutTimer = make_shared<boost::asio::deadline_timer>(boost::ref(*m_ioService));
 
   if (std::getenv("NFD") != 0)
-      m_fwController = make_shared<nfd::Controller>(boost::ref(*this));
+    {
+      if (std::getenv("NRD") != 0)
+        m_fwController = make_shared<nrd::Controller>(boost::ref(*this));
+      else
+        m_fwController = make_shared<nfd::Controller>(boost::ref(*this));
+    }
   else
       m_fwController = make_shared<ndnd::Controller>(boost::ref(*this));
 }