Public-facing schemas #505

We currently have schemas for our IPFS data. However, there is also use for public-facing schemas for our models. These will allow us to render the model data in a way that is agnostic about where the data came from and how it may have been stored there (e.g. it doesn't matter if we got a piece of data from a blockchain event or from an IPFS param). If we combine these schemas with versioned models, we will have the ability to change where data is stored over time and keep the API consistent. (For example, we can move a value from being stored on-chain to being stored in IPFS.)