* Update Postorius, Hyperkitty and django-mailman3.
Also, entrypoint script should compile i18n messages.
* Add git to postorius image.
* Also compile i18n messages in Postorius.
* Add GNU Gettext to the images.
* Do not compilemessages.
* Do not compilemessages.
* Add libffi to all Postorius images.
* Use Django less than a certain version.
* Fix the version constraint.
* Fix uwsgi configuration by using only processes.