greenlight

* Allow uploading larger presentations

This patch allows uploading presentations up to 30MB instead of the
default 1MB. This should prevent users from getting an 401 reply from
Nginx in most cases.

* Update greenlight.nginx

Co-authored-by: Ahmad Farhat <ahmad.farhat@blindsidenetworks.com>
Co-authored-by: Ahmad Farhat <ahmad.af.farhat@gmail.com>