Added password reset to backoffice

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

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

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

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

src/backoffice/templates/backoffice/login.html

src/backoffice/templates/registration/reset_password.html

...ffice/templates/registration/reset_password_complete.html

...office/templates/registration/reset_password_confirm.html

...ackoffice/templates/registration/reset_password_done.html

...backoffice/templates/registration/reset_password_mail.txt

src/backoffice/urls.py

src/backoffice/views/auth.py

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

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

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

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

src/plainui/views.py