Add graphie-to-png to the production-rpc setup

Summary:
Add (what I believe to be) necessary files to install graphie-to-png on the
production-rpc server. This includes cloning, installing dependencies, and
adding the secrets.py in the setup, and adding the required nginx site and init
script.

Test Plan:
  - Not sure how to test?

Reviewers: csilvers

Reviewed By: csilvers

Subscribers: johnsullivan

Differential Revision: https://phabricator.khanacademy.org/D15400