Allow for different networks in both production and staging

[satello]

The current architecture silos mainnet for production and kovan for staging. Production DApps often support multiple networks (see https://github.com/kleros/court).

Re-architect so that the network isn't specific to the deploy environment.

Keep in mind with dynamodb tables that networks need to be separated in some cases. Testnet data can overwrite production data if they are not separate. (see justification tables)

[satello]

Other thing to consider is to re-architect DApps to use the respective Kleros Microservices staging/production URIs for test and mainnets. Drawback here would be support for only 1 testnet.