Summary:
Adds support for `Animated.Value#addListener` for native driven nodes on Android. This is based on work by skevy in the exponent RN fork. Also adds a UIExplorer example.
** Test plan **
Run unit tests
Tested that by adding a listener to a native driven animated node and checked that the listener callback is called properly.
Also tested that it doesn't crash on iOS that doesn't support this yet.
Closes https://github.com/facebook/react-native/pull/8844
Differential Revision: D3670906
fbshipit-source-id: 15700ed7b93db140d907ce80af4dae6be3102135
Summary: Move all JS to a js/ subfolder so we get some overview of this folder again.
Reviewed By: bestander
Differential Revision: D3542598
fbshipit-source-id: 7637133fe4152f4d39e461b443b38510272d5bc8