Having keybindings for side-by-side tiling has been requested for a long time, so add this support now. https://bugzilla.gnome.org/show_bug.cgi?id=648700
Move preferences to GSettings, using mainly shared schemas from gsettings-desktop-schemas. Unlike GConf, GSettings support is not optional, as Gio is already a hard dependency of GTK+. https://bugzilla.gnome.org/show_bug.cgi?id=635378