Documentation

[lorenzb]

This issue is for tracking various things that we should document:

• "I can envision a scenario where a given client wants to prove that a transaction at index x of block y is not transaction z, but instead is transaction z'. I guess this would simply be a proof of inclusion of transaction z' and the business logic around z and z' would have to be handled at a higher customer/library consumer code layer. Maybe we should add some words around that?"