* 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
* Allow to import orders
* seats, subevents
* Plugin support
* Add docs
* Warn about lack of quota handling
* Control interface test
* Test skeleton
* First tests for the impotr columns
* Add tests for all columns
* Fix question validation
* First tabs
* Convert more pages
* Convert question page
* Item form
* Add item_formsets signal
* Revert "Add new signal nav_item"
This reverts commit 1ce613ff89.
* Formset is a word!