Fix integration of celery progress and PDF generation with SPA

aleksis/core/assets/components/SmallContainer.vue

...core/assets/components/celery_progress/CeleryProgress.vue

aleksis/core/assets/components/pdf/DownloadPDF.vue

aleksis/core/assets/components/pdf/pdf.graphql

aleksis/core/assets/messages/de.json

aleksis/core/assets/messages/en.json

aleksis/core/assets/routes.js

aleksis/core/models.py

aleksis/core/schema/__init__.py

aleksis/core/schema/base.py

aleksis/core/schema/pdf.py

aleksis/core/schema/person.py

aleksis/core/urls.py

aleksis/core/util/celery_progress.py

aleksis/core/util/pdf.py

aleksis/core/views.py