Replace application schema with prototypeApplication

[jessicamcinchak]

As we work towards a stable v1, we've left our existing application schema & mocked up a new, more granular rules-based prototypeApplication in parallel for a couple reasons:

• So we can easily share side-by-side/before-after comparisons of what's changing to gather feedback
• To demonstrate how the repository is now structured in a way that supports building, testing & publishing many schemas rather than just one as originally setup

After we've gathered feedback on the prototype, we want to:

• Replace application with prototypeApplication on the main branch
• Do a pre-release (eg v1.0.0-alpha.0) to pre-publish the new spec
• Start exchanging/testing the pre-released spec from PlanX staging environments (still exchanging v0.7.0 on prod?)
• After testing & smoothing out any further bugs with further pre-releases, do a proper v1.0.0 release