Code review comment for lp:~cszikszoy/do/proxy

I'd prefer it if there weren't whitespace changes mixed in here, but I know that can be difficult to do.

If I understand this code correctly, you've extended the Preferences service to also handle system-wide preferences. I'm not sure how good an idea this is - could we instead have something like a SystemConfiguration service that would deal with this sort of system-wide configuration? An advantage I see from that is that the proxy configuration work could get factored out into a platform-neutral place - the proxy setting code is platform independent.

That would also remove the somewhat smelly AddNotify/RemoveNotify addition to IPreferencesService.