- use clientdb config for addon sql files

- do not install/update addons during install/update of ISPconfig. This only leads to lots of trouble

- do not install/update addons during install/update of ISPconfig. This only leads to lots of trouble

- TODO: the server services plugin is not capable of enabling and disabling addon plugins, yet

- removed line that drops the ISPConfig database (and was not executed before due to a sql syntax error)

- improved rspamd handling

Update installer_base.lib.php to remove the creation of postfix self-signed cert prior to ISPConfig to avoid duplicity and time consuming, as it is now replaced and covered in function make_ispconfig_ssl_cert() via symlinks to the related files.

Update installer_base.lib.php to remove support for multi domain since it requires working vhost / conf for the added domains.

Update installer_base.lib.php for ISPConfig to use certbot webroot for webservers and certbot standalone for other servers. Also extend the certs for postfix, dovecot and pure-ftpd-mysql.

Update installer_base.lib.php to fix typo error and add code to extend ISPConfig LE SSL certs to other services that are postfix and pureftpd, if they are installed. The code give user option whether to extend the certs or not.

Update installer_base.lib.php accordingly to [Jesse Norell's suggestion](https://www.howtoforge.com/community/threads/wip-use-certbot-standalone-to-create-lets-encrypt-ssl-certs-for-ispconfig-servers.80449/#post-381238) which is supposedly more prudent.

Update installer_base.lib.php to replace ssl on / off that is already deprecated in Nginx 1.15 with ' ssl' / '' and to change the same in nginx_ispconfig.vhost.master as well.

Update installer_base.lib.php to change if (!@is_dir($le_live_dir) && ($svr_ip != $dns_ip)) to else.