A DHT implementation for Dagger

This DHT implementation is aiming to provide a DHT for Dagger with the following properties

• flexible transport usage with
  • fast UDP based operation
  • fallback to TCP-based operation (maybe though libp2p)
  • support operation on top of libp2p
• flexible message encoding that plays well with the above transports
• provide node lookup, content storage/lookup, and provider storage/lookup operations
  • roughly follow the libp2p-dht specifications from https://github.com/libp2p/specs/tree/master/kad-dht
  • provide compatibility mode with the above specs

Current implementation is based on nim-eth's Discovery v5 implementation.

Base files were copied from status-im/nim-eth@779d767b024175a51cf74c79ec7513301ebe2f46