Create client side prefs that extend the service prefs.

vng=r?

I am adding more prefs on the client-side, specifically hardware acceleration.
It is necessary to catch any bugs of prefs creation. If the Pref singleton is created from the service, it is a 'Pref' type, if it is created from the client-side, the singleton is a 'ClientPref' type. Insidious bugs could ensure if this was not enforced early (someone moves creation code around and triggers this bug). We could just have a proxy that is a mini-factory to enforce this instead, and ensure the creation is of the right object type. But that would be more typing :).