Code review comment for lp:~gandalfn/gala/add-dbus-accelerator-and-input-sources

Sorry for merging, it was easier for me and debian packaging.

for unowned has nullable it was a bad habit I have, for me an unowned always can be nullable since it does not transfer its ownership, not really accurate in fact

I'll watch all you remarks, but I think at term pantheon-desktop needs a gnome-settings-daemon/gnome-session programs which manage this kind of stuff