Support for multiple Fabric Networks

[adecaro]

Currently, FSC's configuration support only one Fabric network at the time.
Support for interoperability scenarios where an FSC node is requested to connect to Fabric peers belonging to different networks is relevant and the goal of this issue.

Tasks:

• generic driver: Hide configuration behind an interface
• support fabric configuration as either the current one or fabric.<name of the newtork>.<etc>
• nwo: generate fabric configuration using the key prefix fabric.default
• fabric-sdk: refactor FNS methods
• nwo: support multiple fabric networks, each FSC node is attached to one Fabric network
• each FSC node is attached to multiple Fabric networks
• two Fabric networks integration test representing a use case