settings_manager is still untested, but much refined.

settings_manager.getsetter.secure(): Register the right deferred object
methods for keychain success and fail callbacks!

settings_manager.get(), .set(): Return the promise object.

settings_manager: provide the means to associate a pretty value with
respective settings values, and to fetch the pretty values given a specific
settings value.
Node.adjust_settings(): Use the settings_manager.  Start on apply_settings.

Still untested, and not yet included control flow.