src: Updating code style to conform (more or less) to ndn-cxx style

Also, adding .clang-format that describes the applied style. Note that
this style requires a slightly customized version of clang-format.
diff --git a/examples/custom-apps/hijacker.hpp b/examples/custom-apps/hijacker.hpp
index a90166d..a794f12 100644
--- a/examples/custom-apps/hijacker.hpp
+++ b/examples/custom-apps/hijacker.hpp
@@ -29,25 +29,24 @@
 
 namespace ns3 {
 
-class Hijacker : public ndn::App
-{
+class Hijacker : public ndn::App {
 public:
   static TypeId
-  GetTypeId ();
+  GetTypeId();
 
-  Hijacker ();
+  Hijacker();
 
   // Receive all Interests but do nothing in response
   void
-  OnInterest (Ptr<const ndn::Interest> interest);
+  OnInterest(Ptr<const ndn::Interest> interest);
 
 protected:
   // inherited from Application base class.
   virtual void
-  StartApplication ();
+  StartApplication();
 
   virtual void
-  StopApplication ();
+  StopApplication();
 };
 
 } // namespace ns3