helper+docs+examples: New helper to simplify link failing

Thanks to Saran Tarnoi for providing base implementation of the code
diff --git a/wscript b/wscript
index c0dbf11..6f200dc 100644
--- a/wscript
+++ b/wscript
@@ -124,6 +124,7 @@
         "helper/ndn-header-helper.h",
         "helper/ndn-face-container.h",
         "helper/ndn-global-routing-helper.h",
+        "helper/ndn-link-control-helper.h",
 
         "apps/ndn-app.h",