Example ngnix configs should be consistent with documentation

[stevepiercy]

On both the 15.x and 16.x branches, we have several nginx configuration examples (default.conf) in each of three folders.

• https://github.com/plone/plone-frontend/tree/15.x/examples
• https://github.com/plone/plone-frontend/tree/16.x/examples

We want to make sure that the configurations are consistent across all projects and are reflected in plone/documentation. See plone/documentation#1349