state-channels: Fix compatibility with JSON RPC

[davidyuk]

https://github.com/aeternity/protocol/blob/master/node/api/examples/channels/json-rpc/sc_ws_basic_open_close.md

JSON-RPC specification doesn't say anything about version field in the root of response/requests objects. If it is needed to store protocol version it can use params, result, or method name to be compatible with JSON RPC.

similar issue: aeternity/AEXs#24