This PR introduces solution for #333 - it adds support for array JSON-RPC payload.
unmarshalMessage tries to unmarshal JSON paylod into *jsonrpcMessage object, and in case of failure, analyzes error and, if it's unmarshalling array error, tries to unmarshal it as an array.
This PR refactors RPC subsystem for status-go:
cleans up two different RPC client implementations (RPCManager and rpc.Client)
creates new package under geth/rpc
moves routing logic into this package (rpc.(*router))
add tests for routing
cleans up NodeManager
Adam Babik
monokh
Ivan Daniluk