src: Refactoring common.hpp and minimizing exposed includes

Face class has relatively large rewrite to hide internals using
Implementor pattern.  As of this commit, <boost/asio.hpp> is not
automatically included whenever ndn-cxx/face.hpp is included.  If it is
needed to directly work with io_service, asio.hpp should be specifically
included.

Change-Id: Ie742b851025b4e3da634eb981319df0f42937855
diff --git a/src/security/conf/checker.hpp b/src/security/conf/checker.hpp
index 1ebcf0d..67ab3b1 100644
--- a/src/security/conf/checker.hpp
+++ b/src/security/conf/checker.hpp
@@ -15,11 +15,14 @@
 #ifndef NDN_SECURITY_CONF_CHECKER_HPP
 #define NDN_SECURITY_CONF_CHECKER_HPP
 
+#include "common.hpp"
+
 #include "key-locator-checker.hpp"
 #include "../../util/io.hpp"
-#include <boost/algorithm/string.hpp>
 
-#include "common.hpp"
+#include <boost/algorithm/string.hpp>
+#include <boost/filesystem.hpp>
+#include <boost/lexical_cast.hpp>
 
 namespace ndn {
 namespace security {