fw+doc: Renaming and extending limit extenstion

SimpleLimits now called PerOutFaceLimits.  Also, there is now
PerFibLimits that is inherited from PerOutFaceLimits and implements
additional check.

Also, this commit includes a couple of tricks to improve documentation
of templated classes (PerOutFaceLimits and PerFibLimits). Not ideal, but
much better than before.
diff --git a/model/fw/ndn-forwarding-strategy.h b/model/fw/ndn-forwarding-strategy.h
index fa42502..cd0d041 100644
--- a/model/fw/ndn-forwarding-strategy.h
+++ b/model/fw/ndn-forwarding-strategy.h
@@ -49,6 +49,11 @@
   static TypeId GetTypeId (void);
 
   /**
+   * @brief Helper function to retrieve logging name for the forwarding strategy
+   */
+  static std::string GetLogName ();
+
+  /**
    * @brief Default constructor
    */
   ForwardingStrategy ();