pomodoro-quick-setting: Allow it to start on screen unlock

Ever so often I forget to turn on the timer. Allow to start it automatically on unlock (and also initial start). Configurable via the prefs plugin.

I've folded in to a patch to clean up g_object_connect but not yet a check as we can do that once phosh-mobile-settings!226 (merged) move to meta-phosh so we can add more checks easily.