Configure production deployment to Google Cloud Run

[bartacc]

These changes were tested with infrastructure code from that PR on my personal Google Cloud account. The website works correctly.

This PR contains:

• You can now easily run production build of frontend in local development. Just run dev.py run-app --prod-frontend (or dev.py serve --prod-frontend if containers are already running). The main difference is that production frontend doesn't have hot reload and it packs all css and all js into one file each, which means that pages load much faster.
• There is now one dockerfile for production and development, which is split into separate stages. It's based on alpine to make the image smaller.
• Static files in production are now stored in a Google Cloud Storage bucket, rather than served directly by Django server.
• I've added a script for manual deployment to production.

TODO later:

• CircleCI deployment to production on each merge to master is currently not configured. I will add it later, but it should be similiar to the current deployment script (probably only authentication commands will change)