The `PrefService` was a refactoring of the `Prefs` class, which was bound to `java.util.Preferences` (see #102 for details). Thus the API is fairly specific to `java.util.Preferences`. Areas to generalize: - [ ] `getters` and `setters` for each type - [ ] `Maps` that only hold `String` values - [ ] `Lists` that only hold `String` values - [ ] Remove the access to global, `Class`-less preferences. These only encourage name clashes for no concrete benefit.