dnfdragora replaces Yumex-DNF

Previous releases of Fedora have included Yumex-DNF as a graphical user interface for package management. Yumex-DNF is no longer under active development and so it has been replaced in Fedora 27 by dnfdragora. dnfdragora is a new DNF frontend that is written in Python 3 and uses libYui, the widget abstraction library written by SUSE, so that it can be run using Qt 5, GTK+ 3, or ncurses interfaces.