core: drop std::function and ndn::Exclude from common.hpp, add ndn::optional

Change-Id: Ie3983d8b6f9929430efd8ada8d942e3f95755cd4
diff --git a/tools/nfdc/cs-module.cpp b/tools/nfdc/cs-module.cpp
index d42b82e..6a3b0b5 100644
--- a/tools/nfdc/cs-module.cpp
+++ b/tools/nfdc/cs-module.cpp
@@ -81,7 +81,7 @@
 
 void
 CsModule::fetchStatus(Controller& controller,
-                      const function<void()>& onSuccess,
+                      const std::function<void()>& onSuccess,
                       const Controller::DatasetFailCallback& onFailure,
                       const CommandOptions& options)
 {