Some work towards LocalDataManager: ClientData class

As part of working on LocalDataManager, I split off the username stuff into a separate class. (Favorite and ReadLater ID's would go in this new class too eventually.)

SharedPreferences needs a Context, so DataManager also needs a Context. So the tests also need to provide a context. I've taken care of all of that so that project and tests all compile again.

I would highly recommend that this is reviewed quickly, and that everyone rebase off of this before doing further code because it will cause headaches otherwise.