Changes for dev:
* Change docker-compose to a more modern version
* Rewrite nginx conf for dev
* Update Helm and Nginx conf
* Properly use env var for mail address and external links

Changes for user:
* Replace <i> tags for text by <em>, <b> by <strong>
* Add aria-hidden to <i> tag for css
* Add some documentation to README (See #16)
* Add basic SEO for public views
* Add legal notice
* Allow user to trigger manually some cron job (See #25)
* Correct non closing tags
* Fix bug when no poster are in the DB
* Fix date warning for PVA cron job