Introducing testnet-generic docker/debian packages instead of berkeley.

This PR introduces changes in packages names and file structure:

- -berkeley package suffix is renamed to -testnet-generic
- testnet-generic packages does not include magic config (config automatically loaded when starting daemon) only devnet.json ledger.
- devnet package won't include mainnet.json (we don't need them since it is not feasible to connect "cross chains", e.g. connect to mainnet with daemon built for devnet and vice versa)
- mainnet package won't include devnet.json, for the same reason as above



