Web: React to 16.x and other dependencies

[abock]

This is still a work in progress, but I am giving up for now. I really want <React.Fragment> and React.createRef<T> in 16.x along with other goodies but I think something is amiss in either DraftJS or the DraftJS Plugins layer:

vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:116 Uncaught Error: addComponentAsRefTo(...): Only a ReactOwner can have refs. You might be adding a ref to a component that was not created inside a component's `render` method, or you have multiple copies of React loaded (details: https://fb.me/react-refs-must-have-owner).
    at invariant (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:116)
    at Object.addComponentAsRefTo (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:23031)
    at attachRef (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:23297)
    at Object.ReactRef.attachRefs (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:23316)
    at ReactDOMComponent.attachRefs (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:2630)
    at CallbackQueue.notifyAll (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:8519)
    at ReactReconcileTransaction.close (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:23171)
    at ReactReconcileTransaction.closeAll (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:4794)
    at ReactReconcileTransaction.perform (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:4741)
    at batchedMountComponentIntoNode (vendor.js?v=8DnmUuUruQyWYkdsqZZD9giKgzdjhZ6thdKOYSZgiy4:9424)

The trace is otherwise useless. I cannot find the culprit, but have audited all of our own ref properties on our components to be RefObject<T> now, so I don't think it's us.