ChainSpec extensions (#3692)

* Add some chainspec tests and make sure we validate it.

* Manual implementation of Extension + Forks definitions.

* Move chain spec to separate crate.

* Allow using ChainSpec with extensions.

* Renames.

* Implement Extension derive.

* Implement Extension for Forks.

* Support specifying fork blocks.

* make for_blocks work

* Support forks correctly.

* Add a bunch of docs.

* Make fork blocks optional.

* Add missing docs.

* Fix build.

* Use struct for check_block params.

* Fix tests?

* Clean up.

substrate/core/consensus/babe/src/lib.rs

@@ -89,7 +89,7 @@ use schnorrkel::{
 	},
 };
 use consensus_common::{
-	self, BlockImport, Environment, Proposer,
+	self, BlockImport, Environment, Proposer, BlockCheckParams,
 	ForkChoiceStrategy, BlockImportParams, BlockOrigin, Error as ConsensusError,
 };
 use srml_babe::{
@@ -1367,10 +1367,9 @@ impl<B, E, Block, I, RA, PRA> BlockImport<Block> for BabeBlockImport<B, E, Block
 
 	fn check_block(
 		&mut self,
-		hash: Block::Hash,
-		parent_hash: Block::Hash,
+		block: BlockCheckParams<Block>,
 	) -> Result<ImportResult, Self::Error> {
-		self.inner.check_block(hash, parent_hash).map_err(Into::into)
+		self.inner.check_block(block).map_err(Into::into)
 	}
 }