use global, static properies in Application for local repo state

The Application class is meant to provide a place to store global state of
the app, so let's use it!  FDroid uses it already, its called FDroidApp, so
the calls will get a lot shorter once in FDroid since KerplappApplication
will be replaced by FDroidApp.

Don't fear the global static properties!  Getters and setters suck often.
Or maybe I've just been too deep in Python these days ;)

refs #3204 https://dev.guardianproject.info/issues/3204