[Frontend-GNOME(-IRC|-XMPP)] Replaced GTK#2 references with GTK#3

Additionally dropped Indicate#, Notify# and Dbus# as they reference glib-sharp
2.12 instead of 3.0. Also Glade# had to be dropped as the new bindings don't
cover Glade at all.
[Frontend-GNOME] Removed Stetic and Glade artifacts