Uses django channels instead of tornado for the autoupdate. Therefore
tornado is nolonger a dependency of OpenSlides (but channels).
This uses websockets instead of SockJS.
Use the flag insecure in the start command to provide static files serving.
Use a new session backend that has a ForeignKey to User.
- Used raw SQL for createing default projector during inital migration.
- Removed default_password and hidden agenda items from autoupdate data for some users.
- Removed old get_collection_and_id_from_url() function.
Added api for groups.
Refactored serializers now using 'id' instead of 'url'.
Rework of tornado autoupdate functionality.
Implemented extra data in SockJS messages.