Verify header justification during import (#76)

* reshuffle consensus libraries

* polkadot-useful type definitions for statement table

* begin BftService

* primary selection logic

* bft service implementation without I/O

* extract out `BlockImport` trait

* allow bft primitives to compile on wasm

* Block builder (substrate)

* take polkadot-consensus down to the core.

* test for preemption

* fix test build

* Fix wasm build

* Bulid on any block

* Test for block builder.

* Block import tests for client.

* Tidy ups

* clean up block builder instantiation

* justification verification logic

* JustifiedHeader and import

* Propert block generation for tests

* Fixed rpc tests

substrate/polkadot/api/src/lib.rs

@@ -28,12 +28,12 @@ extern crate substrate_state_machine as state_machine;
 extern crate error_chain;
 
 use client::backend::Backend;
-use client::blockchain::BlockId;
 use client::Client;
 use polkadot_runtime::runtime;
 use polkadot_executor::Executor as LocalDispatch;
 use substrate_executor::{NativeExecutionDispatch, NativeExecutor};
 use primitives::{AccountId, SessionKey};
+use primitives::block::Id as BlockId;
 use primitives::parachain::DutyRoster;
 
 error_chain! {