(cherry picked from commit a54a784168c023d1f95c2c1ba0cd97659ffbd08c)

# Conflicts:
#	core/admin/Dockerfile
#	core/dovecot/Dockerfile
#	core/nginx/Dockerfile
#	core/none/Dockerfile
#	core/postfix/Dockerfile
#	optional/clamav/Dockerfile
#	optional/fetchmail/Dockerfile
#	optional/radicale/Dockerfile
#	optional/unbound/Dockerfile
#	setup/Dockerfile

- Moved run to bottom of Dockerfile to allow using unmodified / cached states.
- Simplified bash code in deploy.sh.
- Improved the large bash one-liner in CI.yml. It could not handle >9 for 1.x.

Install py3-multidict from repository before installing socrate to avoid the need of gcc during build

It turns out we were all blind and admin *does* use MailuStart

This reverts commit c787e4bd.

This fix https://github.com/Mailu/Mailu/issues/918

Bash shell is used by default in Kubernetes' dashboard console, which is very
useful for admins.

Credit to:
- https://stackoverflow.com/a/19590415/1816774
- https://realfavicongenerator.net/

In case of TLS_FLAVOR=[mail,cert], the user supplies their own certificates.
However, since nginx is not aware of changes to these files, it cannot
reload itself e.g. when the certs get renewed.

To solve this, let’s add a small daemon in the place of
`letsencrypt.py`, which uses a flexible file-watching framework and
reloads nginx in the case the certificates change ….

To facilitate this, the default redirect at / can be disabled, even if
the default remains at redirecting to the webmailer.

The extensions are within the host scope and are read from
$ROOT/overrides/nginx/*.conf.

- Specified seperated /health path in order to allow for healthcheck even if webmail and admin are not seletectd. This also allows healthchecking fom external services like DNS load balancers;
- Make curl not to fail on TLS because localhost is not included in the certificates.