Remove genesis module, add more chain specs and separate out ethereum-specific stuff

Fix State to use secure trie variants.

State::new_contract, camelCase engine params, missing param

Use reorganisation

Introduce `use common::*;` for common stuff (modules that themselves require no other modules in this crate).
Fix build.

Initial Ethash/Block skeleton implementations.

Spec with tested Morden genesis decoder and builtins.