* issue 310 - Added a new property, ignoreSilentSwitch. When true, audio will play even when the silent switch on an iOS device is set to silent. When false, the audio will toggle with the silent switch. Sets the AVAudioSession to either playback or ambient.

* Added ignoreSilentSwitch usage to example app and to readme

* Changed ignoreSilentSwitch to accept two string values, ignore and obey.
This accounts for the case where the user does not want to modify the audio session from a particular video instance. The user would not use the ignoreSilentSwitch property at all in that case.
Also, the audio session will only be updated when the video is unpaused, instead of whenever the video component has updated props. This allows for multiple videos to be on the screen, with the most recent video unpaused (aka played) being the video that has control over the audio session.

* initial support for WPF

* update readme with WPF specific instructions

* remove autogenerated .gitattributes file

* reference RNW NPM package instead of hard-coded local reference

This is related to the comment on #368

* added listener for timedMetadata event.

* added callback in RCTVideo for the timed metadata

* exposing onTimedMetadata to JS

* added forgotten method declaration

* returning array of string values

* added metadata type to the array

* added onMetadata method

* overridden onMetadata method on exoplayer2

* added format of return value from onMetadata

* added function reference in README file

Corrected the instructions for running the example

This PR adds react-native-windows support to react-native-video.  The Video component is implemented with a XAML MediaPlayerElement.  Most of the features implemented by Android (and some additional ones) are implemented by Windows.

Known issues and missing features include:
* onReadyForDisplay event
* local URI convention (e.g., "broadchurch" in examples changed to require("./broadchurch.mp4")
* `playableDuration` in `onVideoProgress` event is always 0.0
* `playInBackground` is not yet supported
* Volume settings are applied, but the UWP control does not handle it properly

* added progressUpdateInterval prop iOS

* add prop to Video.js

* added progressUpdateInterval prop iOS

* add prop to Video.js

* Add Android Expansion File Support

* Added notes for usage with Android Expansion file

* Update README.md

Added notes re: expansion file usage.

* formatting issue fixes

Make visible text *<Video>*  wrapping it with a code block

.default argument for iOS

I could not get the Video component to work by following the provided example. I kept getting an error message saying "React.createElement: type should not be null, undefined, boolean, or number.". When I changed the way I include the component, it started working. It might be related to recent versions of react-native, not sure. You're welcome to modify the suggested text if you like. Thanks for a great piece of work!