"replicate" command

We have a private npm registry in our company I need control over which packages go into the registry. All our machines must install from/publish to the private registry.

Cloning the main npm registry isn't an option and hand-copying packages quickly got tiresome, especially with all the dependencies.

Hence I added a replicate command that replicates packages and its dependencies from the main npm registry into the registry configured in npm config registry.

Ideally some proxy functionality should go into the npm registry but this seems something handy to have anyway.