Add Node Discovery

[wy]

At the moment, Happynodes uses the mainnet.json file from neo-mon project and looks for valid JSON-RPC, P2P or WS connections. However, there are more nodes than the ones in that file.

Since we are running a node through our neo-node sub-project, we should be able to run node discovery and update the list of known addresses and connections.

[f27d]

Protocode:

• Start with list of known addresses
• Start a P2P node or use JSON-RPC to get IPs of other nodes
• Do Reverse lookup to get hostname from IP
• If hostname exists add it to address table (basically a ID->hostname mapping)
• If not hostname exists, add the IP address to the address table - that's the default hostname essentially

[i25959341]

fixed by #64 #63