tools: improve user experience by choosing best certificate
automatically and print final response in a pretty way

ndns-update
 - pick the best certificate to sign the Update automatically
 - support multiple token for content option

ndns-dig
 - enhance output option
 - change behavior of iterative query controller when NS query is NACKed

logger
 - set default logger output to std::cerr

Change-Id: Ib06981c224ccad2a122a4505c84a60977184a55b
diff --git a/src/daemon/name-server.cpp b/src/daemon/name-server.cpp
index b02a423..f796e13 100644
--- a/src/daemon/name-server.cpp
+++ b/src/daemon/name-server.cpp
@@ -138,8 +138,7 @@
                          bind(&NameServer::doUpdate, this, interest.shared_from_this(), data),
                          [this] (const shared_ptr<const Data>& data, const std::string& msg) {
                            NDNS_LOG_WARN("Ignoring update that did not pass the verification. "
-                                         << "Validator cannot fetch certificate from the face "
-                                         << "that used by validator itself to send Interest");
+                                         << "Check the root certificate")
                          });
   }
 }