Update the spec

This should be done someday.

## Documents to check
- [ ] Block-Synchronization-Extension.md
- [ ] CodeChain-Account.md
- [ ] CodeChain-Address.md
- [ ] CodeChain-Coin.md
- [ ] CodeChain-Virtual-Machine.md
- [ ] Consensus.md
- [ ] Digital-Signature.md
- [ ] Hash-Function.md
- [ ] JSON-RPC.md
- Not all the error codes are described.
- `Errors:` to `### Errors`
- Description of `engine_getBlockReward` missing dot(`.`).
- Update `Work` and functions on engine and miner.
- Outdated examples (`chain_getTransaction` has `nonce` argument)
- [ ] Kademlia-Extension.md
- [ ] Key-Share-Extension.md
- [ ] List-of-Network-Id.md
- [ ] Merkle-Trie.md
- [ ] Network-Extension-Protocol.md
- [ ] Node-Discovery-Protocol.md
- [ ] Operate-Extension.md
- [ ] P2P-Protocol.md
- [ ] Parcel.md
- [ ] README.md
- [ ] Script.md
- [ ] Session-Initiation-Protocol.md
- [ ] State-Trie.md
- [ ] Stratum.md
- [ ] System-Extension.md
- [ ] Tag encoding.md
- Why this file name using space instead of bar?
- [ ] Transaction-Propagation-Extension.md
- [ ] Wire-Protocol.md

## Documents not added yet
- #259