AVFoundation player by default for OS X 10.8+

Player based on @kronick's [ofxAVFVideoPlayer](https://github.com/kronick/ofxAVFVideoPlayer) with additions and fixes by @obviousjim and @prisonerjohn (from CLOUDS).

* Updated the project template to include the new classes and frameworks.
* Updated the video player example to take into account asynchronous loading.

I also just noticed that this player does not yet implement frame-by-frame (`firstFrame()`, `nextFrame()`, `previousFrame()` methods).