SSL certificate management
Currently ssl certificates, keys, certificate requests and chaincerts need to be added by copy-n-paste into a vhost configuration. The plesk/odin approach seems to be more comfortable: They use an upload button and certs, keys, etc will be added to a named set of certificates, that can be later chosen in vhost configs. As letsencrypt certificates will be supported in upcoming versions of ispconfig, it would seem wise to create these (if enabled) as such a set, that the user can choose of as described above. It should also be possible to save only the location of a cert instead of it's contents in such a set. Sets of certificates should be swapped out to their own tables, that are referenced by the vhost. IMO that would improve the handling a lot.