window-list: Expand workspace button for Fitts'ability

The workspace button used to extend to the bottom edge, which of
course is A Good Thing (tm) - commit ec8f2691071f broke this when
it added an additional container to the hierarchy, expand the
button again to bring back the old mouse-friendly behavior.

https://bugzilla.gnome.org/show_bug.cgi?id=708247
launch-new-instance: Update for gnome-shell changes
Bump version to 3.13.91

To go along GNOME Shell 3.13.91