Add grandpa telemetry (+ other minor improvements) (#1997)

* Support skipping the interactive purge prompt

Skip it via `cargo run -- purge-chain -y`.

* Fix typos

* Add Grandpa telemetry

* Address comments

* Revert unnecessary version bump

* Version bump to make CI run

* Remove unnecessary cast

* Do not bump version

substrate/core/network/src/consensus_gossip.rs

@@ -315,7 +315,7 @@ impl<B: BlockT> ConsensusGossip<B> {
 			use std::collections::hash_map::Entry;
 
 			let engine_id = message.engine_id;
-			//validate the message
+			// validate the message
 			let (topic, status) = match self.validators.get(&engine_id)
 				.map(|v| v.validate(&message.data))
 			{