Prefs moved into service. Accessed through StumblerService by the client code.
Addressing items from Guilherme's review. Note I left the BuildVersion in the service, as I see it belonging there. Arguably, there should be 2, one for client and one for service, but service version is the most important that I can see.
Merge pull request #6 from garvankeeley/cleanup4

Prefs moved into service