Create new rendertron app engine instance to prerender atila pages for cheaper

[ademidun]

• We currently use rendertron to prerender Atila because it is good for SEO and social media link previews

• Atila App Engine Costs for rendertron are very expensive ($90 month) so we are looking for alternatives
  closes Switch from Google App Engine for SEO serverside/pre rendering #79

• Create an app engine instance atila-rendertron that has a minimum_instance of zero in order to save costs which we will use to prerender our application

• Currently deployed on atila-7-staging.appspot.com, once I get home and can review the code on my macbook pro that we used to create the original rendertron instance on atila-7.appspot.com, then we will replace the atila-7.appspot instance with the new one.

Ignore Below, that was the old way

• A temporary solution is to use the rendertron demo service for now: https://render-tron.appspot.com/

In the rendertron docs and this tutorial they mention that we can use the demo Rendertron /render function, though it's not recommended for production

A demo Rendertron service is available at https://render-tron.appspot.com/. It is not designed to be used as a production endpoint. You can use it, but there are no uptime guarantees.

• Use the demo rendertron URL for prerendering
• Remove firebase deploy --only hosting from circleci build process
• Remove old unused cloud functions
• Temporarily disable app engine instance:
  closes Switch from Google App Engine for SEO serverside/pre rendering #79

[ademidun]

Closing this PR now. Once it has finished deploying in circleci.

1. Check firebase functions cloud logs to make sure that the logs show: { renderUrl: 'https://atila-7.appspot.com/render' }

2. Delete staging instance