Enhancements on German translation files

Enhancements on German translations, originating from issue #4503

See merge request !523

[DNS] Allow free standing @ as hostname

Currently, the regex checking the hostname for adding new DNS records doesn't allow `@` as the hostname. This PR adds support for that for `A`, `AAAA`, `MX` and `TXT` records. Not sure if any other DNS record types allow `@` as hostname, but happy to amend this PR if that's the case.

See merge request !521

added support for newer versions of mariadb-server, removed spaces after ?> of file causing empty lines in cron log, ftp settings added



See merge request !514

Fixed #4425 Variable is initialized as string but later written to as array, throws fatal error in PHP 7.1

Fixed #4444 Error in the template htm /usr/local/ispconfig/interface/web/client/templates/reseller_edit_limits.htm

Fixed #4443 Error in the template htm /usr/local/ispconfig/interface/web/client/templates/client_edit_limits.htm

Fixed #4440 Error in the template htm /usr/local/ispconfig/interface/web/client/templates/client_template_edit_limits.htm

fixed issue with missing bracket

I just realised that in my last patch a bracket was missing.
Sorry for that - here's the fix for it.

See merge request !512

small typo in french translation



See merge request !511