Add support for calendar deletion

[nitboss]

Support to delete a calendar that's no longer needed. Note this does not remove all the associated blocked events from all calendars by design. That can be executed through clean, if required

[L0ndra]

I think that we should remove events from this calendar in all othere calendars as well. Cause clean and sync again takes a while for large amount of events

[berezovskyi-oleksandr]

I believe that we can just ask the user for the events deletion as an additional question