Gear menu cleanup

[Matthias Clasen <matthias clasen gmail com>]

Hi everybody,

we're trying to clean up gear menus across GNOME apps. See
https://wiki.gnome.org/Initiatives/GnomeGoals/GearIcons
for the details. Ideally, we can move away from explicitly specifying
the icon name altogether, and just use a menu button with
direction==none. Even where that is not possible, it should be a
really quick and easy fix to replace the current icon name
(emblem-system-symbolic) by the new one (open-menu-symbolic).


Thanks, Matthias