Add project links

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

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

src/backoffice/templates/backoffice/link/link_display.html

src/backoffice/templates/backoffice/project/create_edit.html

src/backoffice/views/projects.py

src/core/forms.py