Bundle commands separately

[eggplantzzz]

Split code shared by cli.js and console-child.js out into its own bundle

[fainashalts]

@eggplantzzz thanks for putting this PR together! I'm on board with this approach, but command.bundled.js won't be available to unbundled versions of Truffle. I think we can probably just check whether a user is using the bundled version there.

[eggplantzzz]

I used BUNDLE_VERSION which is an environment variable we inject in the bundle.

[fainashalts]

Yes, true about users never having the unbundled versions, though I'd venture that its important for Truffle devs and community contributors to be able to use the unbundled version when needed. I guess I didn't mean actual users. This fix seems to address that just fine! This LGTM, pending tests passing.