add optional nginx configs to make more secure

Add back some items removed in https://github.com/gitlabhq/gitlabhq/commit/8aff39a6d0a63e904ada910900ee07a1c3190a9d but makes them optional so they can be ignored if you want a simple setup experience.
I can remove however I don't believe this relates to OCSP.  See https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html for details. I'm not claiming to be an expert, perhaps the article author @RaymiiOrg can chime in.