With the message tray no longer being a distinctive UI element,
the existing <super>m shortcut for viewing the notification list
is no longer mnemonic. It is also less convenient as it requires
both hands with most keyboards. So make <super>v the new default
to _view_ notifications, which matches the corresponding Windows
default.
The previous default is kept as secondary shortcut to ease the
transition.
https://bugzilla.gnome.org/show_bug.cgi?id=687986
58da16c786