[nemo-qml-plugin-calendar] Add a monthly recurrence on week day position. Contributes to TJC#5565
This merge request aims to allow a new kind of recurrence rule using the position of the day in the week for a monthly recurrence. This is already fully supported in KCalCore but was not available in the middleware. It will allow to implement part of the mockups discussed in this ancient TJC thread: https://together.jolla.com/question/5565/recurring-calendar-entries-more-possibilities-eg-every-4-weeks/
I've added a test to ensure that proper recurrence types are saved and reread from database.
@chriadam, this is still WIP though because the corresponding MR in calendar closed sources has not been worked on yet, and it may require to change one or two things here if not properly thought.