[Feature] Generate blueprints

[thomassnielsen]

This is a pretty big one, with many steps. Checkboxes for broad strokes:

• Figure out how the UI should work
• Figure out a way to list available blueprints (addons may add more)
• Implement MVP (pick blueprint, textfield for arguments)
• Implement full UI

[stefanpenner]

Figure out a way to list available blueprints (addons may add more)

we should add ember help --json to ember-cli so tooling can consume. This help printing internals should actually just start using the JSON format, and passing it off to a humanized printer to emit the current stuff, and the raw for --json

[thomassnielsen]

@stefanpenner do you think it is possible to implement this with an addon first, or should one look directly at implementing it in ember-cli? Trying to assess the scope of this.