Create dhparams when ssl is enabled

After Logjam and #578 (closed) we've allowed users to supply dhparams.

Consider creating this automatically when ssl is enabled.

cc @jacobvosmaer

One of the reasons for removing Diffie-Helman key exchange from our default cipher suite (in favor of elliptic Diffie-Helman), for me, was to avoid having to think about generating DH params for users. It can be done of course but I would not rush to add it. :)

No rush, that is why I added 7.13 milestone and said Consider :)

Milestone changed to 7.14

Only one request to add this in over period of 2 months so I think for now I will call this WONTFIX. We can revisit this if the interest for it picks up.

Status changed to closed