Count down the seconds until a screenshot is taken in the window title
This way the user knows by the progressbar and by the changing
number when the screenshot is going to be taken.
Reviewers: Spectacle, ngraham, davidre
Reviewed By: Spectacle, ngraham, davidre
Subscribers: broulik, ngraham, davidre
Differential Revision: https://phabricator.kde.org/D21651