startup: Adding example upstart scripts (e.g., for Ubuntu Linux)

Change-Id: Ia43e0e5e83d54d4f5bff2120ca3424b43849feb2
Refs: #1188
diff --git a/contrib/upstart/nfd-watcher.conf b/contrib/upstart/nfd-watcher.conf
new file mode 100644
index 0000000..392af52
--- /dev/null
+++ b/contrib/upstart/nfd-watcher.conf
@@ -0,0 +1,13 @@
+# nfd-watcher.conf
+#
+# Restarting NDN Forwarding Daemon on network connectivity changes
+
+start on (net-device-up or
+          net-device-removed or
+          net-device-changed)
+task
+
+script
+  status nfd | grep -q start/ || stop
+  restart nfd
+end script