misc centos 8 fixes

See merge request ispconfig/ispconfig3!996

Example csv import email script.

See merge request !988

Update php_fpm_pool.conf.master - removed php_admin_value[cgi.fix_pathinfo]

See merge request !981

Allow updating sysuser modules through remoting

See merge request !984

Reconfigure incron if the PHP version changes

See merge request !983

Don't use short array syntax

See merge request !982

Update php_fpm_pool.conf.master - removed php_admin_value[cgi.fix_pathinfo] = 0 which cause in fpm chroot errors: Access to the script has been denied (see security.limit_extensions). This settings is obsolete for newer PHP version. More info: https://www.howtoforge.com/community/threads/php-fpm-chroot-with-cgi-fix_pathinfo-0-causes-access-to-the-script-has-been-denied.84071/

Add additional option to frontend, #5325

See merge request !906

#4617 dont trigger change for fastcgi php version reload

See merge request !958

Exclude IP's from maintenance

See merge request !975

Disable stats button if stats are none

See merge request !972

Improved backup in `userzip` mode

See merge request !976

Feature/backup copies

See merge request !974

Load remoting classes from modules

See merge request !978

Feature/add api example system config get

See merge request !977

Enable Proxy Protocol - Patch for 3.1

See merge request !933