keyboard: Port custom shortcut dialog to GtkGrid

https://bugzilla.gnome.org/show_bug.cgi?id=709057
keyboard: Port typing tab to GtkGrid

https://bugzilla.gnome.org/show_bug.cgi?id=709057
keyboard: Port shortcuts tab to GtkGrid

https://bugzilla.gnome.org/show_bug.cgi?id=709057