src: Reorganizing source code in preparation to merge NRD code

Note that as of this commit, there are several changes in location of
compiled binaries in `build/` folder:

* `nfd` has been moved to `build/bin/nfd`
* `unit-tests` has been split into `unit-tests-core` and `unit-tests-daemon`

Change-Id: I2c830c117879edbaa5457d6423c13f0273285919
Refs: #1486
diff --git a/daemon/main.cpp b/daemon/main.cpp
index de9511e..4ff0264 100644
--- a/daemon/main.cpp
+++ b/daemon/main.cpp
@@ -33,7 +33,7 @@
 #include "mgmt/face-manager.hpp"
 #include "mgmt/strategy-choice-manager.hpp"
 #include "mgmt/status-server.hpp"
-#include "mgmt/config-file.hpp"
+#include "core/config-file.hpp"
 
 namespace nfd {