Support a production relay

[jkaczman]

We need to upgrade our system in several ways to support a proper production relay:

• An API that advertises what protocols the server supports. Based on the supported protocols, we interface with the server in different ways. The DIY server maintains general functionality, and the production server expands on that subset with additional protocols (and perhaps swaps some out).
• Support these new protocols that the server broadcasts, e.g. content-addressed storage, anonymity-enhancing services, etc.
• Bandwidth should be taken into consideration. Techniques such as P2P can help in cases of low latency and/or high resolutions.
• Changes to the mobile app allowing easy access / indication of this new relay and the options for it.
• Make note of these new protocols and options in our documentation.