Refactor app view

Introduce a top level view for navigating between the inbox and the
installer, enabling an in-window relink flow. Navigation is driven
through the openInbox and openInstaller global events.

// FREEBIE

js/views/install_view.js

@@ -73,6 +73,7 @@
         },
         close: function() {
             this.remove();
+            Whisper.events.trigger('openInbox');
         },
         events: function() {
             return {