State planning across timezone changes

[ondryaso]

When time(zone) changes while the service is running and StatePlannerBackgroundService is sleeping, having previously received a nextTransition state, the planner service fires events at wrong times – because it doesn't have any way of knowing that the amout of time to wait should be adjusted.

This should be partially solved by properly handling timezones (as previously mentioned in #55). Also, I think that an additional check should be introduced in StatePlannerBackgroundService after it resumes that would reassure that the state has actually started.