Update to Polymer 2, perf improvements, refactor

[davidrleonard]

Gets things ready to fork a new version that will be used as the AppHub "microapp seed" from our team.

• Moves to Polymer 2.x native style components for the app code
• Refactors data to make things more "app like"
• Improves perf (esp TTCI time-to-consistently interactive) by lazy loading views on demand, deferring imports
• Updates build process to rely on polymer build for all bundling/transformation
• Adds new folder structure, a bit like the one described here for React apps, and adds some documentation to the README to explain it
• Updates README a bit

@randyaskin @mdwragg plz review. Also if you have ideas for more perf wins that would be very helpful.

[davidrleonard]

@katemenkhaus if you have time to glance at CSS that would help too. thanks.

[watfordgnf]

Any traction on this? I'm migrating a project based on the sample app on the v1 system to Polymer 2, and it would be nice to have a functional example.