Load as little as possible in index.js for the skinner

Imports are optimized to be concurrent/async by webpack, which means that when the old index.js referenced the Lifecycle from the react-sdk it caused the app to explode. This is because in another branch the Lifecycle references a class member of a skinnable component, leading to the skinner complaining that the skin hasn't been loaded.

To work around this, we've shoved all the app stuff to a new app.js file, leaving just the skinning and some early bootstrap work in the index.js