feat: extend schedule by hours and days

[sebhoerl]

This PR updates the RunExtendSchedule tool. Before, one could only set a maximum extension period in seconds. Now one can define either

--end-time 619200

All departures that fit inside this horizon when extended by multiples of 24 hours will be duplicated (multiple times if fitting).

For convenience, instead one can also define the duration in hours and days:

--days 7 --hours 4

This would extend the schedule by seven days and four additional hours on the following day.