ReservationOccurrence bulk creation and cleanup
Post rebase fixes
Added overlapping helpers to datetime utils
Overlap methods added to ReservationOccurrence
Fixed ReservationOccurrence bulk creation with TZ
Generalized BarList2Dictionary helper

* Created group_list method
* Removed unnecessary class
* Renamed iterators.py
Prevent overlap checks between different rooms
Moved iterdays to indico.util.date_time with rrule
Added missing RoomBars class