Option to customize FTP info displayed to users

[stefanpejcic]

In OpenPanel UI on /ftp for the FileZilla and cyberduck templates + the FTP server/port shown on the page, we should allow admin to customize them.

for filezilla/cyberduck should read templates if exist in:

/etc/openpanel/ftp/filezilla.conf
/etc/openpanel/ftp/cyberduck.conf 
/etc/openpanel/ftp/server.conf (for server displayed and port)

for filezilla/cyberduck files when user downloads them in the gui, we should read those files if present, repalce placeholders and serve. else if files invalid or not present, keep what we have now and render it completely in backend.

[stefanpejcic]

added in 2.0.1 and documented https://github.com/stefanpejcic/OpenPanel/blob/main/website/docs/articles/user-experience/customizing-ftp-client-templates-and-server-info.md