ISPConfig itself does not read nor interpret this header, but there might be other
server components like PHP that might interact with it so I'll disable it just to be sure.

After enabling "Rewrite HTTP to HTTPS" and "Lets Encrypt SSL" the RewriteCond and RewriteRule got on the same line, becourse of an failing newline

This reverts commit 7827db36

Set default env[PATH] and env[HOSTNAME] since it is cleared by default setting clear_env = yes in php-fpm

- disabled database logging of sql reconnect errors, fixed #3974

- remove certificate renew config on domain deleting

- added 'certbot' to which command (if letsencrypt is not installed as system package, but certbot is)

add optional arrays for service-name to function system->getinitcommand and also a parameter to check if the current service exists (mandatory if you use an array)

Removed ubuntu1604.lib.php which is not required anymore.

- Introduced confid in $distver array to separate the config and class for a distribution in the installer.
- Cleaned up the dist detection.