OpenEthereum 4.0 Core

This crate contains the most fundamental open ethereum types and should have no dependencies on any other crates in this project.

Its purpose is to define a unified type model for common data types used across various components of the system.

It is expected that almost all other crates will have this one as a dependency.

Design notes:

This crate implements large integer types. It is inspired by Parity's ethereum-types, however its trimmed down version is used for use with serde-rlp serialization and it also fixes compilation issues for rust 2018 edition.
All serialization to and from JSON, RLP (or the proposed Blob Serialization) should be handled at the Serde level and new formats should be just serde drivers.
Currently exported types are
- large ints: U128, U256, U512
- hashes: H128, H160, H256, H264, H512
- fundamental concepts: Block, Transaction, any additional functionalities to those objects should be added through traits. Please do your best not to duplicate those types. If you feel a strong urge to create a new fundamental concept type please ask around the team first.