* New models
* CRUD UI
* UI for adding/removing team members
* Log display for teams
* Fix invitations, move frontend
* Drop old models (incomplete)
* Drop more old stuff
* Drop even more old stuff
* Fix tests
* Fix permission test
* flake8 fix
* Add tests fore the new code
* Rebase migrations
This simplifies providing an `event_view` method which works as
decorator for presale/ views (e.g. for plugins), providing passing
requests with event and organizer context if possible, and re-routing or
failing appropriately otherwise.