Feature: Tool to mutate ROOT package.json with specified archetype tasks

[coopy]

Strawman:

• [ ] Mutate ROOT package.json and add in any archetype commands prefixed with npm:
• [ ] Do collision detection and warn / rename with e.g :backup for existing commands that would be rewritten
• [ ] Do https://github.com/FormidableLabs/builder/issues/81 at the same time (warn if archetype implements any npm lifecycle tasks).