RFC: 171 CloudFront Redesign (#174)

* RFC: 0171 CloudFront Redesign - initial rough ideas

* Iteration #2 of the API, sans the Lambda@Edge functionality.

Still in draft state, but hopefully getting closer.

* Lambda@Edge API v1, plus some of the open questions and other sections filled in.

* Added detailed design section, including before/after examples

* Proper namespacing in the examples, and updated the open questions

* Minor update to force pull request refresh

* Minor changes per feedback; removing the 'draft' tag

* Distribution.for* syntactic sugar

* Removing Distribution.behavior, keeping origin->behavior nesting consistent

* Minor API updates per feedback and lessons learned from implementation

* Added implementation note for capturing behavior ordering