Libp2p identify protocolVersion should be set to the name of the chain

[tomaka]

https://github.com/paritytech/substrate/blob/e434882d5dbf3f3f6085cb7f1d017dbc4ac11f0a/client/network/src/peer_info.rs#L98

This should be set to the id of the chain rather than just /substrate/1.0.
It is used purely for debugging, so it's very much not important, but the name of the chain is more appropriate than "substrate".

I've also opened w3f/polkadot-spec#652 so that all Polkadot nodes use the same value.