Add basic equivocation detection pipeline schema (#2338) (#2341)

* Move finality Engine to finality_base folder

* Define SubstrateFinalityPipeline

Extract basic parts of SubstrateFinalitySyncPipeline into
SubstrateFinalityPipeline

* Add equivocation detection pipeline

* Fix comment

bridges/relays/client-westend/Cargo.toml

@@ -17,3 +17,4 @@ bp-westend = { path = "../../primitives/chain-westend" }
 # Substrate Dependencies
 
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master" }

bridges/relays/client-westend/src/lib.rs

@@ -22,6 +22,7 @@ use relay_substrate_client::{
 	Chain, ChainWithBalances, ChainWithGrandpa, RelayChain, UnderlyingChainProvider,
 };
 use sp_core::storage::StorageKey;
+use sp_session::MembershipProof;
 use std::time::Duration;
 
 /// Westend header id.
@@ -52,6 +53,8 @@ impl Chain for Westend {
 impl ChainWithGrandpa for Westend {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str =
 		WESTEND_SYNCED_HEADERS_GRANDPA_INFO_METHOD;
+
+	type KeyOwnerProof = MembershipProof;
 }
 
 impl RelayChain for Westend {