Gio: modernize DBus bindings
Gio: modernize DBus bindings

Remove tabs, use modern GError bindings, remove comments that
are no longer relevant.

https://bugzilla.gnome.org/show_bug.cgi?id=669350

pixunil/cjs,pixunil/cjs,endlessm/gjs,endlessm/gjs,mtwebster/cjs,djdeath/gjs,endlessm/gjs,pixunil/cjs,pixunil/cjs,djdeath/gjs,mtwebster/cjs,djdeath/gjs,mtwebster/cjs,mtwebster/cjs,djdeath/gjs,pixunil/cjs,mtwebster/cjs,endlessm/gjs,djdeath/gjs,endlessm/gjs