Add client/server mode support to Kademlia DHT #387
Description
Add client/server Kademlia DHT mode separation. Nodes running as clients are not added to the routing tables of the server nodes, and records/providers are not published to them. This improves Kademlia health in networks with nodes running behind NATs/firewalls without an accessible p2p port by not trying to reach such nodes during Kademlia operation.
libp2p spec: https://github.com/libp2p/specs/blob/master/kad-dht/README.md#client-and-server-mode