Create fcl json transport layer module

[orodio]

Related to: https://github.com/onflow/flow-js-sdk/issues/676

A json native way of communicating with the Access Node is in development, this issue covers the development of the transport layer to bridge fcl/js-sdk and an access node via json. It should be assumed that this will be the primary/default way for the js-sdk and fcl to communicate with the access node in the future.