More app-friendly event description (#6684)

* More app-friendly event description

* change origin -> owner

* checked all decl_event! and changed decriptions.

* annotated parameter names for remaining events

substrate/frame/im-online/src/lib.rs

@@ -276,11 +276,11 @@ decl_event!(
 		<T as Trait>::AuthorityId,
 		IdentificationTuple = IdentificationTuple<T>,
 	{
-		/// A new heartbeat was received from `AuthorityId`
+		/// A new heartbeat was received from `AuthorityId` [authority_id]
 		HeartbeatReceived(AuthorityId),
 		/// At the end of the session, no offence was committed.
 		AllGood,
-		/// At the end of the session, at least one validator was found to be offline.
+		/// At the end of the session, at least one validator was found to be [offline].
 		SomeOffline(Vec<IdentificationTuple>),
 	}
 );