Well-formedness properties

There are many properties that are currently part of the rules, which don't really fit into any particular rule thematically, and don't depend on anything but the signal. We could call these 'well-formedness properties', and bundle all of them into one place for them to be checked. This should improve consistency and readability of the STS rules.

Here are some:
- Addresses
- Byron: `bootstrapAddrsSize <= 64`
- Maybe `networkID = NetworkID`, though this needs access to global constants
- Transactions
- `txADhash ≡ map hash txAD`
- Maybe `txins ≢ ∅`
- Maybe `coin mint ≡ 0`
- PParams has `paramsWellFormed`
- More for blocks (once we have those), maybe others