Use canonical network names for zos network files

[jbcarpanelli]

Fixes zeppelinos/zos-cli#342

Implemented a small function that takes the network id from web3.version and returns the network name based on this list.
I only added the most used networks, and if the network id doesn't match inside the switch clause, then I'm naming it as dev-NN, being NN the network id retrieved by web3, as proposed by @spalladino.

[spalladino]

Great, loved how succint the change is! Note that the integration tests are failing, since they still use the old naming for checking the proxy addresses (I think you'll need to modify run.js). We can merge as soon as that's fixed.