Reformat, add translations and fix gql queries

aleksis/apps/chronos/frontend/components/AmendLesson.vue

.../apps/chronos/frontend/components/AmendLessonOverview.vue

...is/apps/chronos/frontend/components/AmendedLessonCard.vue

...is/apps/chronos/frontend/components/LessonInformation.vue

aleksis/apps/chronos/frontend/components/amendLesson.graphql

aleksis/apps/chronos/frontend/index.js

aleksis/apps/chronos/frontend/messages/de.json

aleksis/apps/chronos/frontend/messages/en.json

aleksis/apps/chronos/managers.py

aleksis/apps/chronos/model_extensions.py

aleksis/apps/chronos/models.py

aleksis/apps/chronos/rules.py

aleksis/apps/chronos/schema/__init__.py

aleksis/apps/chronos/util/predicates.py