Implement ApplyConfiguration in terms of XRandR calls.
Error checking is done before actually committing the configuration.
If mutter is using one of the other monitor config backends, an
error is reported and nothing happens.
https://bugzilla.gnome.org/show_bug.cgi?id=705670
Turns out that even if two outputs say that they can be controlled
by a given CRTC, you can't configure them in the same CRTC unless
they are marked as "possible clones" one of the other.
This can further restrict the configuration options, so we need
to expose this limitation in the DBus API.
https://bugzilla.gnome.org/show_bug.cgi?id=705670
This new interface will be used by the control center and possibly
the settings daemon to configure the screens. It is designed to
resemble a simplified XRandR, while still exposing all the quirks
of the hardware, so that the panel can limit the user choices
appropriately.
To do so, MetaMonitorMode needs to track CRTCs, outputs and modes,
so the low level objects have been decoupled from the high-level
MetaMonitorInfo, which is used by core and API and offers a simplified
view of HW, that hides away the details of what is cloned and how.
This is still not efficient as it should be, because on every
HW change we drop all data structures and rebuild them from scratch
(which is not expensive because there aren't many of them, but
at least in the XRandR path it involves a few sync X calls)
https://bugzilla.gnome.org/show_bug.cgi?id=705670
