Proposal: Using libp2p for network-related communication

libp2p aims to be a catch-all solution for all things p2p-network.

That means that adding components such as mDNS doesn't require any careful development for each solution on it's own, but rather enables application creators to pick from a gigantic library of existing modules that implement capabilities such as mDNS, kademila DHT, TCP and UDP networking support

I'm making this proposal, to see whether and how it can be implemented

The plan to enable it would be to:
- First integrate py-libp2p networking and run a seperate swarm besides the current swarm, but on the same port (this should be possible by first checking if the incoming data is multistream or TLS)
- Integrate all custom networking components into the libp2p swarm using modules
- Switch the other swarm off for good, once the functionality of the libp2p swarm is confirmed and a majority of users has upgraded

// cc @filips123 @imachug @blurHY