Send back better error when disconnecting because of invalid peer headers

[jondubois]

Expected behavior

If a peer tries to connect with missing required header fields, a node should send back a descriptive error message.

Actual behavior

If a peer tries to connect to us with missing headers, we disconnect them with a generic 'BadConnectionError'.
This generic error is useful for rejecting malicious peers (as not to give away too much info) but it's not ideal in this case.

See #2064 (diff)

Steps to reproduce

Try to connect to a node with missing headers as part of the WebSocket connection query string.

Which version(s) does this affect? (Environment, OS, etc...)

1.0.0