* Event feedback functionality and related commits:
* blackness and isort and flake8 - this branch does not have pre-commit so I forgot :/
* finish backoffice management of eventfeedback
* add username to eventfeedback detail panel when viewed in backoffice
* Add feedback url to elm schedule. Fix access when user is anonymous. Remove print statement.
* one prefetch_related call to rule them all
Co-authored-by: Víðir Valberg Guðmundsson <valberg@orn.li>
* update font-awesome to 5.1 and add fab- and fa-regular icons, fixed#244
* also handle slugs when dealing with SingleObjectMixin CBV views, fixes#248
* add missing trailing slash to bar/menu
* add missing trailing slash on event slugs, fixes#245
* fix a lot of stuff related to proposal URLs. actually display them on speaker and event detail pages. show the urltype icons. better messages on update and delete pages. fix 500 error when reapproving events. fix bug that made urls multiply when reapproving event. fixes#246 and fixes#247