Consider Strengths and Weaknesses of Dynamic UTXO Typing

[JoshOrndorff]

This issue is to discuss the strengths and weaknesses of the current way in which UTXO are dynamically typed.

The thoughts are explained mostly in the docs for the dynamic_typing module.

One strength not previously mentioned is that dynamically typing allows a convenient way to scrape for inehrents a la #130 (comment)

An alternative strongly typed approach would be to have each tuxedo piece provide an type to be aggregated. Simple pieces may have no types (and use ()) or a single type (like Coin) and use it directly. More complex pieces may have multiple types and will provide an enum themselves.