Chain-beacon/relay interface

[Shadowfiend]

More in the relay's concern than the chain's concern, this is about how the chain and beacon/relay interact. Some open questions:

• Use promises.
• Need handlers for group registration, relay entry appearance, and relay request appearance.
• Need to be able to call relay entry submission (triggering relay entry appearance above).

[Shadowfiend]

I think we're done here 🎉