eg, for IRC, show private messages, but not channel messages https://bugzilla.gnome.org/show_bug.cgi?id=614972
Also reorganizes the notification layout to use an StScrollView; very tall notifications are now scrolled instead of just taking up more and more of the screen. https://bugzilla.gnome.org/show_bug.cgi?id=608999
And suppress libnotify-based notifications from Empathy https://bugzilla.gnome.org/show_bug.cgi?id=608999
