* Add client-traits crate
Move the BlockInfo trait to new crate
* New crate `machine`
Contains code extracted from ethcore that defines `Machine`, `Externalities` and other execution related code.
* Use new machine and client-traits crates in ethcore
* Use new crates machine and client-traits instead of ethcore where appropriate
* Fix tests
* Don't re-export so many types from ethcore::client
* Fixing more fallout from removing re-export
* fix test
* More fallout from not re-exporting types
* Add some docs
* cleanup
* import the macro edition style
* Tweak docs
* Add missing import
* remove unused ethabi_derive imports
* Use latest ethabi-contract
