Document usage of ssl parameters
Change name to ssl_certificate and ssl_certificate_key,

Since that is what nginx uses too. Lets not use arbitrary shortened
words
Introduce a "listen 443 ssl;" when certificates provided
Let template use the  longer variable names
Merge branch 'feature/ssl' into develop

* feature/ssl:
  Let template use the  longer variable names
  Introduce a "listen 443 ssl;" when certificates provided
  Change name to ssl_certificate and ssl_certificate_key,
  Document usage of ssl parameters