Summary:
This diff adds support for native spring animations on iOS. This overlaps some spring work done by kmagiera on the Android side of things.
**Test plan (required)**
Run UIExplorer NativeAnimated examples before and after - compare the results. Pay special attention to the spring examples.
Closes https://github.com/facebook/react-native/pull/9048
Differential Revision: D4056088
Pulled By: foghina
fbshipit-source-id: a593408cb61cb850572bab4a0884f7157cece656
Ryan Gomba