... and add example 'htpasswd' file

(and with spaces it's easier to copy-paste in a console for debugging)

...'build', 'clair' and 'docker-bench-security'

CI seems to have started from the wrong path in previous build: 
https://gitlab.utc.fr/picasoft/projets/dockerfiles/-/jobs/883015

These vulnerabilities were also fixed by 5b6bd312

CVE-2020-8492 reported by Clair in previous build: 
https://gitlab.utc.fr/picasoft/projets/dockerfiles/-/jobs/883005

This comes from 'libpython2.7', which is one of many unnecessary 
dependencies that get installed with 'cron' dy default

This change was already in prod since some days, but not commited

Revert this commit to enable backups again.

Cf. 21c1e819

Revert this commit to enable backups again.

Backups were run every six hours, but due to the huge increase in the 
size of our DB (Docker volume 'etherpad-db' takes 47 GB at this time), 
backups take almost 3h30 to complete, slowing down the entire instance 
during that period.

Cf. https://team.picasoft.net/picasoft/pl/9w6bq59o93npix1m1kzwpwmqxy

X)

Cette fois ça devrait être bon !

> Dotdeb is an extra repository providing up-to-date packages for your 
Debian 8 “Jessie” servers