ShellApp+ShellGlobal: unify app launch context code

Extend shell_global_create_app_launch_context() with the required
parameters and use that for shell_app_launch() too.

https://bugzilla.gnome.org/show_bug.cgi?id=669603

js/ui/components/telepathyClient.js

@@ -1339,7 +1339,7 @@ const AccountNotification = new Lang.Class({
             let cmd = 'empathy-accounts --select-account=' +
                 account.get_path_suffix();
             let app_info = Gio.app_info_create_from_commandline(cmd, null, 0);
-            app_info.launch([], global.create_app_launch_context());
+            app_info.launch([], global.create_app_launch_context(0, -1));
         }));
 
         this._enabledId = account.connect('notify::enabled',