Use PureOS g-c-c

First step at folding things back into PureOS proper

byzantium.yml

@@ -14,6 +14,9 @@ gnome-clocks:
   url: https://source.puri.sm/Librem5/debs/gnome-clocks.git
 gnome-contacts:
   url: https://source.puri.sm/Librem5/debs/gnome-contacts.git
+gnome-control-center:
+  url: https://source.puri.sm/pureos/packages/gnome-control-center.git
+  branch: pureos/master
 gtherm: {}
 gtk:
   url: https://source.puri.sm/Librem5/debs/gtk.git