* dht: add configuration to persist/load state to/from a file * dht: avoid network request for 'get' if a 'listen' op is synched for the same key * dht: performance/memory usage improvements * proxy: handle value expiration/refresh * proxy: reliability improvements * proxy: performance improvements * dhtrunner: avoid failing if socket can't be bound for one of ipv4/ipv6 * improved unit tests