Reorganize nginx configs to share most elements

[rfay]

From @rfay on March 22, 2018 21:2

What happened (or feature request):

Currently the entire nginx config is repeated for every project type, which is unnecessary and confusing and hard to maintain. They should be reorganized so that only the key things that are different are in the separate configs.

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else do we need to know:

Related source links or issues:

Copied from original issue: drud/docker.nginx-php-fpm-local#63

[rfay]

A key aspect of this task is to make it easier for our users to make small changes to the config. However, we have to make it so they can understand the big picture if they need to.