Summary: Use fbjni for safer and easier jni bridging. This diff includes all of fbjni as it currently does not live as its own open source project. The code was copied from the react-native open source distribution.
Reviewed By: ritzau
Differential Revision: D3764065
fbshipit-source-id: 7ff566af314dcb5279460c322c476ef6f6ed8131
