edit static page, delete static page

src/backoffice/forms.py

src/backoffice/locale/de/LC_MESSAGES/django.po

src/backoffice/locale/en/LC_MESSAGES/django.po

src/backoffice/templates/backoffice/staticpage_detail.html

src/backoffice/templates/backoffice/staticpage_form.html

src/backoffice/urls.py

src/backoffice/views/pages.py