Try to get grandpa tests compiling again (#1121)

* Revert "start to refactor block import wrapper a bit"

This reverts commit b919de49e1a82422a0870b66100832d531174771.

* Refactor grandpa stuff to get tests almost compiling

* Fixes after rebase

* Fixes merge compile errors

substrate/node/runtime/src/lib.rs

@@ -465,7 +465,7 @@ impl_runtime_apis! {
 
 
 	impl GrandpaApi<Block> for ClientWithApi {
-		fn grandpa_pending_change(digest: DigestFor<Block>)
+		fn grandpa_pending_change(_digest: DigestFor<Block>)
 			-> Option<ScheduledChange<NumberFor<Block>>> {
 			unimplemented!("Robert, where is the impl?")
 		}