Merge branch '78-tls-context' into 'master'

Resolve "Verify TLS certificate of Plugin Server"

Closes #78 

Please note that this adds basic TLS verification (a big improvement over the current status!) but there is still room for enhancement: certificate pinning or CA pining, disabling TLS1.0, and probably some more. I'm leaving those for a separate MR (and probably further discussion)

See merge request !6