Support native captions in html5 tech.

Don't auto-add the textTrackDisplay component.
Add a 'featuresNativeTrack'. Currently hardcoded to false for everything
except the html5 tech.
Add textTracks and addTextTrack methods to html5 tech.
Proxy player level methods to tech if we're using native tracks.
Fix up track menu items to work with spec tracks or vjs tracks.

This is the beginning of step 1 for the [revamp](https://github.com/videojs/video.js/issues/1655) of text tracks.

* [x] Native tracks, if available
* [x] Re-use non-native otherwise
* [x] Chrome Support
* [x] Firefox support
* [x] iPad Support
* [x] Android support
  * [x] Chrome for Android -- works like desktop chrome
  * [x] Native Android Browser
* [x] IE Support
  * [x] IE11
  * [x] IE10
  * [x] IE9
  * [x] IE8 
* [x] Tests
Yeah, I was wondering about the tech switching case. That techs at least won't switch unless the source is changed, so the question is should tracks persist after a new source is set. I'm not sure how the video element handles that but I would be tempted to say that no matter what the video element does, if you set a new source you have to provide new tracks for the source at the same time. If tracks (including dynamically created ones) need to persist then that would create a much bigger headache for us as far as translating native tracks to non-native tracks in a tech switch.