RGB: Fungible assets update: burn, replacement, renomination

[dr-orlovsky]

Proposal to LNP-BP/LNPBPs#38

Burn & reissue procedure named "replacement" and organized as a linear sequence within a linear sequence of epochs. Each epoch can replace maximum 100% of its original issue/supply (created at genesis or with a secondary issue ancestor).

Each issue (primary in genesis and secondary with issue state transition type) defines up to a single epoch seal.

When the seal is closed, a Epoch state transition must be created, which

1. MUST has no metadata;
2. MAY define a single next epoch seal (otherwise it will mean that no further replacement epochs are allowed), and
3. MUST define a single replacement seal.

Replacement seals are closed with Replacement state transition type, which

1. MAY optionally provide some binary proof data (with empty data validated as valid and the rest of data are validated as invalid until some possible future standard update);
2. specifies an amount to be reissued/replaced;
3. MUST define up to a single replacement seal.

Replacement state has a special validation procedure, which fails if the sum of all replacements within the epoch exceeds the original issued amount.

Upd: Use replacement workflow for asset recovery: LNP-BP/LNPBPs#50

[dr-orlovsky]

PruneProof -> HistoryProof

[dr-orlovsky]

Add fields:
BurnedUTXOs: UTXO
ProofFormat: enum()