v2 Addon spec as default

Documenting some of the things that need to be done before v2 spec is the default for new addons, from a discussion with @ef4:

• prepublish tool that converts from colocated templates to explicit setComponentTemplate
• Recruit from the learning team to write guides on how to create a v2 addon, and when v2 addon should be used vs v1
• Update ember-cli-update to also update nested test-apps for v2 addons

[ef4]

Yes, and @rwjblue has convinced me that we should push for the monorepo version as the default.

The main benefit of not using a monorepo has historically been the ability for people to point their package.json dependencies directly at your repo, but since most v2 addons will have a build step anyway that already doesn’t work. So there’s not really a downside to using a monorepo.

[kellyselden]

I’m glad we are talking about this. I was planning on writing an RFC for monorepo addon + dummy app (as work time allows).