More refactoring to reduce global event dependencies

All Whisper.events listeners are now defined and bound in background.js,
and we no longer need global methods for opening the inbox and
conversation views, as those are handled by AppView or internally by
InboxView.

// FREEBIE

js/panel_controller.js

@@ -25,10 +25,6 @@
     };
     var inboxWindowId = 'inbox';
 
-    window.openInbox = function(options) {
-        Whisper.events.trigger('openInbox', options);
-    };
-
     window.setUnreadCount = function(count) {
         if (count > 0) {
             window.setBadgeCount(count);
@@ -39,8 +35,4 @@
         }
     };
 
-    window.openConversation = function(conversation) {
-        Whisper.events.trigger('openConversation', conversation);
-    };
-
 })();