Keccak256-based structured commitments

This library provides utilities for defining hashes of structured data, in a way that supports nested data structures and automatic domain separation (ie, two structures with different fields will never feed the same input into the hash function).

WARNING

Implementing Committable using RawCommitmentBuilder is a manual process that should be done carefully. In the future, we will provide a macro to automatically implement Committable in a reasonable way, but for now, use this library with caution.