Make standalone registration more accessible

Add buttons for switching between the linking flow and the standalone
registration flow. The button and standalone registration are only
availble in a development environment.

// FREEBIE

js/views/app_view.js

@@ -9,6 +9,8 @@
           this.installView = null;
         },
         events: {
+            'click .openInstaller': 'openInstaller',
+            'click .openStandalone': 'openStandalone',
             'openInstaller': 'openInstaller',
             'openInbox': 'openInbox',
         },