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

Update installer_base.lib.php to use php instead of cli / shell command in renaming files and creating symlinks.

Update installer_base.lib.php as per the discussions / feedback in the thread at https://www.howtoforge.com/community/threads/wip-use-certbot-standalone-to-create-lets-encrypt-ssl-certs-for-ispconfig-servers.80449 by adding check whether the hostname fqdn A record has the same ip with the server before requesting for Let's Encrypt SSL standalone certs.

Update installer_base.lib.php to fix lines 2439-2441; remove line with .csr; use $conf['hostname'] if not localhost or empty.

Update installer_base.lib.php to use certbot standalone to create SSL certs for ISPConfig server(s).

Patch 4

See merge request ispconfig/ispconfig3!833

Patch 3

See merge request ispconfig/ispconfig3!832

Patch 2

See merge request ispconfig/ispconfig3!831

Patch 1

See merge request ispconfig/ispconfig3!830

Add ci test for php syntax

See merge request ispconfig/ispconfig3!827

# Conflicts:
#   .gitlab-ci.yml