Proposal creation and evaluation to plug into BFT (#77)

* 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

* network and tablerouter trait

* use statement import to drive creation of further statements

* Fixed rpc tests

* custom error type for consensus

* create proposer

* asynchronous proposal evaluation

* inherent transactions in polkadot runtime

* fix tests to match real polkadot block constraints

* implicitly generate inherent functions

* add inherent transaction functionality to block body

* block builder logic for polkadot

* some tests for the polkadot API

polkadot/primitives/src/parachain.rs

@@ -121,6 +121,13 @@ impl Slicable for DutyRoster {
 	}
 }
 
+/// Extrinsic data for a parachain.
+#[derive(PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[cfg_attr(feature = "std", serde(rename_all = "camelCase"))]
+#[cfg_attr(feature = "std", serde(deny_unknown_fields))]
+pub struct Extrinsic;
+
 /// Candidate parachain block.
 ///
 /// https://github.com/w3f/polkadot-spec/blob/master/spec.md#candidate-para-chain-block