always load local manifest at startup

This gives proper content from the start, without requiring the user to check
for updates to get something out of the app.

This also gives us proper URLs for manifest and assets updates.

www/js/index.js

@@ -116,7 +116,33 @@ var app = {
 
     // Device ready callback
     onDeviceReady: function() {
+        var request = new XMLHttpRequest();
+        request.open('GET', '../index.json');
+        request.onload = function() {
+            if (request.status != 200) {
+                /* this should never happen */
+                app.utils.setLoadingMsg("Initialisation de l'application : erreur de chargement");
+            } else {
+                var new_manifest = JSON.parse(this.responseText);
+                for (var attr in new_manifest.meta) {
+                    if (new_manifest.meta.hasOwnProperty(attr)) {
+                        app.manifest.meta[attr] = new_manifest.meta[attr];
+                    }
+                }
+                app.manifest.title = new_manifest.title;
+                app.manifest.content = new_manifest.content;
+                app.manifest.pages = new_manifest.pages;
+                app.onDefaultManifestLoaded();
+            }
+        };
+        request.send();
+    },
 
+    onDefaultManifestLoaded: function() {
+        app.initApplication();
+    },
+
+    initApplication: function() {
         // Init fileSystem
         app.initFileSystem();