Added a server migration mode setting which will be used to prevent that LE tries to recreate certs during a server migration.

The cipher suites are only set now for ISPConfig's own vhost, the intermediate security profile from Mozilla is used here.

Improved ispconfig.vhost for apache so that the sethandler directive does not affect other software which is accessed trough aliases.

ISPConfig itself does not read nor interpret this header, but there might be other
server components like PHP that might interact with it so I'll disable it just to be sure.

This reverts commit 008ef889.

https://mozilla.github.io/server-side-tls/ssl-config-generator/

Changed behaviour of UFW installation. Do not enable it by deafult as the firewall will get enabled autmatically when a firewall record gets added in ispconfig. Enabling it without that record, the Firewall would lock out the user on next reboot.