- Drop relative size bits, seems not that useful or widely used
- Use a KFontDialogPrivate class instead of KFontDialog::Private (see:
https://mail.kde.org/pipermail/kde-frameworks-devel/2015-August/025956.html)
- Port to QDialog
- Drop the fontList parameter in the ctor, it's not useful, 99% of the times
users of this class called the static getFont() methods
- Make the parent QWidget * the last param. in the ctor, a la Qt API
See https://phabricator.kde.org/D27808 for more details.