Code review comment for lp:~gotwig/simple-scan/headerbars

I've pushed a branch to lp:~robert-ancell/simple-scan/optional-headerbar-ui that shows how you can have both the header bar and the toolbar in the same .ui file and conditionally use each one.

You disable the HeaderBar by using Gtk.Window.set_titlebar (null). This doesn't work in GTK+ 3.10 because it doesn't have [1] but I will backport that to Ubuntu.

I'm also open to changes that do the UI in the .vala files. Vala is not too bad at being concise in generating UI and it makes the patches easier to read.

[1] https://git.gnome.org/browse/gtk+/commit/?h=gtk-3-12&id=8db2ba425aaff107faaa4c7468be63f8ef2fa8e9