display: adapt to the new model for display configuration

The way we apply the new configuration changed, in that we are
expected to call the apply() method of GnomeRRConfig ourselves,
and that takes care to call to mutter, show the confirmation
dialog, etc.

https://bugzilla.gnome.org/show_bug.cgi?id=705573
wacom: adapt to GnomeRR API changes

GnomeRR now returns the EDID IDs as strings directly, so we don't
need to convert them to compare to the settings. Also, we don't
need to filter disconnected outputs, it's done by mutter now.

https://bugzilla.gnome.org/show_bug.cgi?id=705573
CcRRLabeler: don't crash when not running under X

If running under wayland, we can't use an X property notify
to look at workarea changes.
Currently, workarea is not part of the wayland protocol, so don't
bother and just don't crash.

https://bugzilla.gnome.org/show_bug.cgi?id=705573