[Shotwell] Support for desktop not using client side decoration?

[Sebastien Bacher <seb128 ubuntu com>]

Hey shotwell hackers,

Git recently got some visual refresh, that's nice to see, it seems that
GtkHeaderBar has used as decoration in an unconditional way though.
That's an issue for !gnome-shell desktops (Unity, xfce, ...), is there
any plan to make those decoration conditional ?

Cheers,
Sebastien Bacher