Bug Fixes in KDE-PIM
Recurring to-dos work again.
Before KCalCore, the date of the current to-do occurrence was stored in the RECURRENCE-ID property. With KCalCore, that had to be removed, because the RECURRENCE-ID property was needed to implement the recurrence-id features.
This commit makes Todo::dtRecurrence() to be saved in an X-property, so it persists, like it did in KDE 4.4.