With workspace thumbnails, we don't switch workspaces when dragging windows
between workspaces or adding new workspaces, so we also shouldn't switch
on launch.

 * Add workspace parameters to shell_doc_system_open(),
   shell_app_activate, shell_app_open_new_window()

 * Pass a 'params' object when activating items in the overview with
   two currently defined parameters: workspace and timestamp. (timestamp
   is only implemented where it is easy and doesn't require interface
   changes - using the global current timestamp for the shell is almost
   always right or at least good enough.)

https://bugzilla.gnome.org/show_bug.cgi?id=640996