core: move common.hpp to core/

Headers in core/ are now included as `#include "core/*.hpp"`.
This allows NFD to rely less on include paths when used as a submodule in
another codebase, such as ndnSIM and NFD-Android.

refs #3127

Change-Id: Ia38f3c97427e17ff7b5401281f1fe875b5d5313e
diff --git a/daemon/fw/asf-probing-module.cpp b/daemon/fw/asf-probing-module.cpp
index 097a372..d60a215 100644
--- a/daemon/fw/asf-probing-module.cpp
+++ b/daemon/fw/asf-probing-module.cpp
@@ -25,7 +25,7 @@
 
 #include "asf-probing-module.hpp"
 
-#include "random.hpp"
+#include "core/random.hpp"
 
 #include <boost/random/uniform_real_distribution.hpp>