Geoclue network info enhancements

[Bastien Nocera]

Heya,

In git master, I've moved most of the crappily horrible shell to get
network information into a shared src/libconnectivity.la, and
implemented non-crappy versions if one uses NetworkManager.

There's still a bug in NetworkManager itself:
https://bugzilla.gnome.org/show_bug.cgi?id=623160

And a couple of helpful shortcuts, potentially:
https://bugzilla.gnome.org/show_bug.cgi?id=617192
https://bugzilla.gnome.org/show_bug.cgi?id=617191

I also updated the dbus-glib minimum requirements to 0.86, which should
fix the D-Bus errors handling bugs, and fixed the crasher when
NetworkManager is available but there's no devices handled.

Cheers