Fixed English strings concerning agenda items and organizational items and their relation. Fixed #1271.
Portable build fix: Install missing roman package.
Fixed #1275 (Creating assignment pdf failed)
Cleaned up some widgets and the base.css. Removed icon definitions.
Updated requirements_production.txt.
Updated test coverage minimum.
Renamed 'permission_required' to 'required_permission' etc.

Renamed method and attribute of openslides.utils.views.PermissionMixin. Renamed attribute of widgets and main menu entries. Fixed #1160.
Replace own CKeditor with dedicated app