* Upgrade Django to 3.0 and other dependencies to recent versions
* Fix otp version contsraint
* Remove six dependency
* Resolve some warnings
* Fix failing tests
* Update django-countries
* Resolve all RemovedInDjango31Warnings in test suite
* Run isort
* Fix import
* Update PostgreSQL version on travis
* Data model and migration
* Some backwards compatibility
* CRUD for checkin lists
* Show and perform checkins
* Correct numbers in table and dashboard widget
* event creation and cloning
* Allow to link specific exports and pass options per query
* Play with the CSV export
* PDF export
* Collapse exports by default
* Improve PDF exporter
* Addon stuff
* Subevent stuff, pretixdroid tests
* pretixdroid tests
* Add CRUD API
* Test compatibility
* Fix test
* DB-independent sorting behavior
* Add CRUD and coyp tests
* Re-enable pretixdroid plugin
* pretixdroid config
* Tests & fixes
