Allow an option to hide the roster with no systray icon
I really like the Ubuntu messaging indicator menu; there is a Gajim plugin out there, and it works great.
However, now that I can control Gajim fully via the messaging indicator, there is no need for it to show it's systray icon. Currently Gajim enforces this when you want to be able to hide the roster window.
I would like to suggest a hidden "always_hide_roster" option that can be used if an alternative, custom way is used to access the roster via Dbus, like the messaging menu plugin.
(In [fdbb8050d2a2]) add an option to allow hidding roster even if systray is not shown. Fixes #6930