Updated for Gnome Shell 3.8/3.10.

  * Updated zeitgeist.js library. We now communicate through Gio.DbusProxy
    because GDbus is deprecated in newer Shell versions.
  * Updated the Popup list view, for changes in Shell's API.
  * Updated application launching to work through Shell.AppSystem.

This has been tested on 3.10 but has been also enabled for 3.8, which should
work. There may be bugs, beware.