[Merge] lp:~straemer/software-properties/fix-for-1058070 into lp:software-properties

[Robert Roth]

The improvement looks fine, and it makes software properties a "singleton" app, allowing it to run only one instance per session.

However it does the single-instance handling via a custom dbus interface. Gtk Application [1] can do single-instance handling since gtk 3.6, along with other maybe-useful features, like appmenu, etc. I don't know whether there are any best-practices regarding single-instance apps, but if it has been added to the core gtk platform, maybe we could make use of that (I guess that GObject introspection works with the gtkapplication class too, so it shouldn't be too tricky)

[1] http://developer.gnome.org/gtk3/3.6/GtkApplication.html
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https://code.launchpad.net/~straemer/software-properties/fix-for-1058070/+merge/140075
Your team Ubuntu Core Development Team is requested to review the proposed merge of lp:~straemer/software-properties/fix-for-1058070 into lp:software-properties.