EIP-xxxx: genesis.json standardization

Discussion thread for a new EIP that offers an optional standard for the network genesis file.

There are a number of outstanding EIPs that are unable to refer back to the cannonical way to define a genesis, because it does not exist. Examples include:

etc.

I propose doing this in an iterative fashion, adopting a json schema that defines the status quo, with the expectation that it would be built upon for future improvements to genesis management. Concepts like:

Named EIPs in the protocol schedule
Initial state provided outside of json, for large pre-states
Deprecation of older features

Are all popular among client devs, and should be pursued once a baseline standard is established.