Time was incorrectly displayed when opening the "Change date and time"
window due to invalid string conversion. Fixed by using different
string converting function which does not use printf underneath.
This PR fixes:
-several explicit uses of `new` that were not matched by `delete`
-dangling `CalendarTimeItem`s
-reset of focus on the `allDayEventCheckBox` check/uncheck
-exiting the app form `allEventsWindow` on `KEY_RF`
- add ChangeDateAndTimeWindow,
- extract EventTimeItem to common widgets folder
and rename it to TimeWidget,
- extract EventDateItem to common widgets folder
and rename it to DateWidget,
- replace timeWidget with common TimeWidget
in NightshiftWindow,
- refactor time setting in
DesktopMainWindow and TopBar,
- Remove dead code from EventManager
(GetNextAlarmTimestamp and HandleAlarmTrigger)