In /etc/nginx/nginx.conf we set client_max_body_size at 32M, so we
can upload larger files, of arbitrary size if application use chunked
uploads.

32M is the value suggested by the Phabricator configuration:
https://secure.phabricator.com/book/phabricator/article/configuring_file_storage/#configuring-upload-limit

Reference: http://nginx.org/en/docs/http/ngx_http_core_module.html#client_max_body_size

Fixes T457.

• Syntax checked through |nginx -t`.
• Result checked on Wolfphab and DevCentral, two Docker containers using this image.