Reintroduce Firewall GTK+ Applet

[poma]

Current Firewall Applet - Qt5 based, has too many unnecessary dependencies.

For those using GTK+ based Desktop Environments there is a very elegant solution, reintroduction of the Firewall GTK+ Applet.

Not only that GKT+ based Applet works just as well as its Qt5 counterpart,
but it also provides genuine GTK+ Look and Feel within modern GTK+ Desktop.

Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1404328