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/common-pch.hpp b/src/common-pch.hpp
new file mode 100644
index 0000000..7b3c03a
--- /dev/null
+++ b/src/common-pch.hpp
@@ -0,0 +1,41 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/**
+ * Copyright (c) 2013-2014,  Regents of the University of California.
+ * All rights reserved.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ *
+ * This file licensed under New BSD License.  See COPYING for detailed information about
+ * ndn-cxx library copyright, permissions, and redistribution restrictions.
+ */
+
+#ifndef NDN_COMMON_PCH_HPP
+#define NDN_COMMON_PCH_HPP
+
+// If compiler supports precompiled header, this header should be compiled and include
+// before anything else
+
+#include "common.hpp"
+
+// STL headers to precompile
+#include <vector>
+#include <list>
+#include <set>
+#include <algorithm>
+#include <map>
+#include <sstream>
+#include <fstream>
+#include <exception>
+#include <map>
+
+// Other useful headers to precompile
+#include <boost/lexical_cast.hpp>
+#include <boost/asio.hpp>
+#include <boost/date_time/posix_time/posix_time.hpp>
+
+#include <boost/iostreams/detail/ios.hpp>
+#include <boost/iostreams/categories.hpp>
+#include <boost/iostreams/stream.hpp>
+
+#endif // NDN_COMMON_PCH_HPP