use seperate config for amavis-dkim-config even is the systems uses a monolith config to prevent overwriting the key-config during updates

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.