Autopeering improvements

[alexsporn]

• Use a more explicit namespace for DHT discovery.
• Use a shrinking map for holding neighbors to avoid long-term leaks.
• Use a distinct network-name everytime the docker or feature network snapshots are created to avoid collisions in autopeering.
• Use autopeering bootstrap peers in the docker network to speed up peer discovery.
• Let nodes wait until node-1 is healthy before starting up. This, together with the autopeering improvements speeds up the network bootstrapping.
• Introduced a max number of peers for autopeering. If set to 0 autopeering won't be started.
• Stop advertising for autopeering if the max number of peers is reached.