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/install_view.js

@@ -26,6 +26,7 @@
                 installFinalButton: i18n('installFinalButton'),
                 installTooManyDevices: i18n('installTooManyDevices'),
                 ok: i18n('ok'),
+                development: window.config.environment === 'development'
             };
         },
         initialize: function(options) {