Remove Parent Hash to Session mapping (#928)

* Adds a SigningContext type

* Bump spec versions

* Fixes requested changes

* Bump ParachainHost api_version and guard signing_context call

* Improve error message

* If there is no signing_context api use default value

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

polkadot/runtime/test-runtime/src/lib.rs

@@ -24,7 +24,7 @@ use rstd::prelude::*;
 use codec::{Encode, Decode};
 use primitives::{
 	AccountId, AccountIndex, Balance, BlockNumber, Hash as HashT, Nonce, Signature, Moment,
-	parachain::{self, ActiveParas, AbridgedCandidateReceipt}, ValidityError,
+	parachain::{self, ActiveParas, AbridgedCandidateReceipt, SigningContext}, ValidityError,
 };
 use runtime_common::{attestations, claims, parachains, registrar, slots,
 	impls::{CurrencyToVoteHandler, TargetedFeeAdjustment},
@@ -319,6 +319,7 @@ impl parachains::Trait for Runtime {
 			Self::KeyOwnerProofSystem as KeyOwnerProofSystem<(KeyTypeId, Vec<u8>)>
 		>::IdentificationTuple;
 	type ReportOffence = Offences;
+	type BlockHashConversion = sp_runtime::traits::Identity;
 }
 
 impl offences::Trait for Runtime {
@@ -536,6 +537,9 @@ sp_api::impl_runtime_apis! {
 					Err(_) => None,
 				})
 		}
+		fn signing_context() -> SigningContext {
+			Parachains::signing_context()
+		}
 	}
 
 	impl fg_primitives::GrandpaApi<Block> for Runtime {