Punish offline validators, aura-style (#1216)

* make offline-reporting infrastructure more generic

* add a listener-trait for watching when the timestamp has been set

* prevent inclusion of empty offline reports

* add test for exclusion

* generate aura-offline reports

* ability to slash many times for being offline "multiple" times

* Logic for punishing validators for missing aura steps

* stub tests

* pave way for verification of timestamp vs slot

* alter aura import queue to wait for timestamp

* check timestamp matches seal

* do inherent check properly

* service compiles

* all tests compile

* test srml-aura logic

* aura tests pass

* everything builds

* some more final tweaks to block authorship for aura

* switch to manual delays before step

* restore substrate-consensus-aura to always std and address grumbles

* update some state roots in executor tests

* node-executor tests pass

* get most tests passing

* address grumbles

substrate/core/client/src/client.rs

@@ -1170,6 +1170,27 @@ impl<B, E, Block, RA> BlockBody<Block> for Client<B, E, Block, RA>
 	}
 }
 
+impl<B, E, Block, RA> backend::AuxStore for Client<B, E, Block, RA>
+	where
+		B: backend::Backend<Block, Blake2Hasher>,
+		E: CallExecutor<Block, Blake2Hasher>,
+		Block: BlockT<Hash=H256>,
+{
+	/// Insert auxiliary data into key-value store.
+	fn insert_aux<
+		'a,
+		'b: 'a,
+		'c: 'a,
+		I: IntoIterator<Item=&'a(&'c [u8], &'c [u8])>,
+		D: IntoIterator<Item=&'a &'b [u8]>,
+	>(&self, insert: I, delete: D) -> error::Result<()> {
+		::backend::AuxStore::insert_aux(&*self.backend, insert, delete)
+	}
+	/// Query auxiliary data from key-value store.
+	fn get_aux(&self, key: &[u8]) -> error::Result<Option<Vec<u8>>> {
+		::backend::AuxStore::get_aux(&*self.backend, key)
+	}
+}
 #[cfg(test)]
 pub(crate) mod tests {
 	use std::collections::HashMap;