Merge caching changes into master

[WIP] Prevent errors on iOS when using text tracks with caching

Fixes a crash when using the cache & sideloaded text tracks together due to the tracks on the asset not being available. Re-visit when someone with more expertise on the cache can look at it.

Reorganize README

[WIP] Update ExoPlayer to version 2.8.2

Feat/ontimedmetadata android

ios Caching Support

Update NewtonSoft JSON to match react-native-windows version

Android - Keep screen on

Fix HLS Playlists (only support mp4, m4v and mov file extension)

Add debug logging for guiding library consumers about why their video is not cached

Expose DefaultLoadControl parameters Android ExoPlayer

I'm guessing this was a bug as it doesn't make sense that we would set paused to true if the video is playing, and not paused if it wasn't. I believe this is a safe change since we only release the player when the app is closing or we detach (which is going away shortly). We need this since we release the player in order to apply new bufferConfig settings.