feat: accept cli args via json and package.json

[davidmurdoch]

This enables doing ganache --config my-config.json where my-config.json is

{
  "wallet.totalAccounts": 5
}

This also enables setting the same config object in the project's package.json under the "ganache" field. e.g.,

{
  // ... rest of package.json
  "ganache": {
    "wallet.totalAccounts": 5
  }
}

We probably want to kick this one down the road, as the preferred way of specifying options is to set "wallet": {"totalAccounts": 5}}. We disabled yargs' dot-notation feature because of the way yargs parses dot-notation arguments didn't work well for us (I can't remember exactly what the problem was right now); and now the side effect is that it doesn't parse these config files the way we want.