WIP: Interceptors and Contect changes

[sirtimbly]

Inspired by the documentation on tao.js.org I am re-considering the validator flow. A rendering method should be able to register interceptors for validation. If an interceptor returns a falsy value then execution continues, if it returns any value that value is treated as a new context for the state to calculate.

Users who write rendering functions should be able to create adhoc state calculations as well. They should be registered in the main app and they just affect values in their own purview, some key perhaps that identifies the terms to be calculated and affected.

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