Adds and handles callback from the "Calibrate" button.
When clicked, we get the current calibration and feed
it in to the calibration utility. After it completes
we get back a modified calibration and an indication
of success. If it was successful we apply the changes,
if not, we ignore the modifed calibration.
https://bugzilla.gnome.org/show_bug.cgi?id=657423
