npm init ionic

`npm@6` has a new mechanism for initializing projects powered by npx: https://docs.npmjs.com/cli/init

Instead of maintaining a global/local CLI, we could utilize a package whose sole purpose is to create an Ionic project, and then have the Ionic CLI be local.

Start with the npm@6 init documentation linked in the issue, focusing on the npx-based initialization flow. Review how the current Ionic CLI is distributed and determine whether a dedicated project-creation package with a local CLI is feasible; done requires a settled implementation approach, not just a proposal.

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