Modification of CcnxFace interface and unification of CCNx applications via common CcnxApp class

Moving functionality of interest limits from PIT to Face.

!!! Code compiles, but probably doesn't work !!!
diff --git a/model/ccnx-fib.cc b/model/ccnx-fib.cc
index a2d8b4b..bd3cd67 100644
--- a/model/ccnx-fib.cc
+++ b/model/ccnx-fib.cc
@@ -216,6 +216,27 @@
   return entry;
 }
     
+void
+CcnxFib::Delete (const CcnxNameComponents &prefix, Ptr<CcnxFace> face)
+{
+  NS_LOG_FUNCTION (this << prefix << face);
+
+  CcnxFibEntryContainer::type::iterator entry = find (prefix);
+  if (entry == end ())
+    return;
+
+  modify (entry,
+          bind (&CcnxFibEntry::RemoveFace, _1, face));
+  if (entry->m_faces.size () == 0)
+    {
+      erase (entry);
+    }
+}
+
+void
+CcnxFib::DeleteFromAll (Ptr<CcnxFace> face)
+{
+}
 
 std::ostream& operator<< (std::ostream& os, const CcnxFib &fib)
 {