MonitorManager: add EDID properties to the output DBus description

Add "edid-file", if we have one (in the KMS case, where we can point
people to the right sysfs file), or "edid" with inline data.
These are needed by colord to build the default ICC profile for
uncalibrated displays.

https://bugzilla.gnome.org/show_bug.cgi?id=705670