Summary:
This replaces all uses of `React.createClass` with `createReactClass` from the `create-react-class` package, attempting to match use of `var` and `const` according to local style.
Fixes#14620
Refs #14712
Closes https://github.com/facebook/react-native/pull/14729
Differential Revision: D5321810
Pulled By: hramos
fbshipit-source-id: ae7b40640b2773fd89c3fb727ec87f688bebf585