Move more params to the common section.

[rphmeier]

• gasLimitBoundDivisor
• registrar
• blockReward
• eip155Transition

Also, Miner will now only seal the first block of a chain if there are no hard forks included.

[keorn]

Since we plan to make Parity more generic over state machines is there be a better place for those?

[rphmeier]

@keorn actually, that is the entire purpose of this PR. Now AuthorityRound and Tendermint have no configuration other than consensus-specific. CommonParams and Builtins will become part of the EthereumMachine, and engines will own only a Machine and their internal members for consensus.
To ease integration, I plan to have a blanket impl<E: Engine<EthereumMachine> + ?Sized> E { ... } in the ethcore crate.

The Ethash engine still has a bunch of its own hard forks which could also be extracted. But for now it was easier to leave them be, as we won't do much prototyping with that engine.

Eventually (perhaps before 1.8) we could change the "params" section of the spec, where CommonParams is parsed from, to configure the state machine to be used. But generalizing the infrastructure around Engine (sync, client, RPC, etc) will be much harder than generalizing Engine itself.

[keorn]

True, CommonParams is mostly Ethereum specific anyway.