Check that configurations where monitors are disabled are properly
used. Also test that old configurations with explicitly disabled
outputs are migrated properly.
https://bugzilla.gnome.org/show_bug.cgi?id=787629
So far some basic testing, including:
* Test that the migrated configuration is applicable
* Test that a monitors.xml with multiple configurations are translated
* Test rotation
* Test tiled monitor discovery (well, test a made up tiled monitor
configuration since I don't have a real one)
https://bugzilla.gnome.org/show_bug.cgi?id=777732