Option to run Discovery V4 and V5 on the same port

[alexb5dh]

• Added adapter to send Lantern.Discv5 messages using Netty connection (IDatagramChannel), instead of built-in one (UdpConnection)
• Process incoming Lantern.Discv5 message using a new Netty handler (NettyDiscoveryV5Handler), if v4 implementation (NettyDiscoveryHandler) didn't manage to recognize the format.
• Moved connection-management code from DiscoveryApp to a new DiscoveryConnectionsPool, since these can now be shared, depending on the versions enabled and ports configuration.

~~Depends on https://github.com/Pier-Two/Lantern.Discv5/pull/105 being published on Nuget~~