This adds tests for following features/scenarios:
* Recurrent appointments and events of all (repetition) types.
* Recurrent appointments with a duration of more than 24 hours.
* Overlapping recurrent appointments.
* Recurrent items and leap years.
* Recurrent items with an end date.
* Recurrent items with exceptions.
Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>
