fix play() on ipad does not start playing and double click issue

I have seen some issues with mediaelement and manually starting a video on the ipad. 

I have changed the code that a simple play call on the player ensures that a load() is called once before.
To implement this logic all play() calls on the media element are replaced with a player.play() method call.
 
There was also another issue when you clicked on a player it starts to play only after a second click.
I figure out, that the ipad didn't fake a click event when you clicked the video element the first time. But i triggers a touchstart event. The big play button now listen on both the click and touchstart event.