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.h b/model/ccnx-fib.h
index 2bd131c..84d618d 100644
--- a/model/ccnx-fib.h
+++ b/model/ccnx-fib.h
@@ -277,7 +277,19 @@
   CcnxFibEntryContainer::type::iterator
   Add (const CcnxNameComponents &prefix, Ptr<CcnxFace> face, int32_t metric);
 
-  // void resetProbing();    //reset needsProbing field for every FibEntry
+  /**
+   * @brief Remove reference to a face from the entry for `prefix`. If entry had only this face, the whole
+   * entry will be removed
+   */
+  void
+  Delete (const CcnxNameComponents &prefix, Ptr<CcnxFace> face);
+
+  /**
+   * @brief Remove all references to a face from FIB.  If for some enty that face was the only element,
+   * this FIB entry will be removed.
+   */
+  void
+  DeleteFromAll (Ptr<CcnxFace> face);
 
 protected:
   // inherited from Object class