[gnome-control-center] (9 commits) ...display: Ensure configuration has the expected type

[Benjamin Berg <bberg src gnome org>]

Summary of changes:

  0c4e84e... display: Ensure we have a primary monitor after all were di (*)
  ae22f72... display: Prevent error when serializing invalid configurati (*)
  21bb641... display: Reset resolution when switching configuration type (*)
  98d2065... display: Make rebuilding variable a counter (*)
  e387b3b... display: Only enforce single mode when desired by UI (*)
  b2f1d48... display: Add unusable monitors to dropdown and disable swit (*)
  defbceb... display: Simplify configuration type and UI selection logic (*)
  f45dcff... display: Ensure at least one display is enabled (*)
  b26a8bd... display: Ensure configuration has the expected type (*)

(*) This commit already existed in another branch; no separate mail sent