WIP: Use AVFoundation without using AVPlayer

This is needed to enable Multimedia player support on iOS.  Instead of
using the highlevel AVPlayer API, and render multimedia to AVPlayerLayer
objects, we use AVAssetReader and decode and play the media ourselves.
This allows us to have full control over both the decoded audio and
video streams.

This is only a commit of the work I've done so far.  The Video should
play without audio, and without the audio sync support.  I hope to fix
the many issues present next week.

Change-Id: I8515017464a4daf3c0423bc9278c424a92cc53af