* Allow sync reorg up to pruning history size

* Peer difficulty tracking

* Abort downloading block if received with NewBlock

* Set pruning history to 1200

* Renamed history size field

* configurable CHAIN_ID

* set CHAIN_ID for Ethereum Classic

* derive(Binary) -> binary

* ethcore types refact

* fixup ethcore

* make binary optional

* fix common types

* fix updater

* remove condition

Closes #3861

- Move Updater into its own crate.
- Change ethcore -> parity in authors, homepages and licenses.