Add network verification

The app doesn't try to get or update the data if the phone is not
online.

mobile/www/index.html

@@ -104,13 +104,13 @@
 
 <!-- Your custom app scripts -->
 <script src="js/app.js"></script>
+<script src="js/index.js"></script>
 <script src="js/database.js"></script>
 <script src="js/graph.js"></script>
 <script src="js/feclass.js"></script>
 <script src="js/stats.js"></script>
 <script src="js/feclass-stats.js"></script>
 <script src="js/comparator.js"></script>
-<script src="js/index.js"></script>
 
 </body>
 </html>