Preload and ns play

* Make sure that the preload boolean gets set correctly based on the value specificed in html5 (unless preload=='none', set preload to true).
* If we are preloading, we want to initialize the netconnection and netstream but *not* play. So, immediately after the ns is initialized and called `play` to add in the video url, we pause the ns.
* We are are autoplaying, or play has been called, resume the ns.
* Fire `loadeddata` after `loadedmetadata` in onmetadata
* Only have onmetadata run once per video
* Allow setting preload and autoplay programmatically.
I realize this PR has nothing to do with this but `ON_BUFFER_FULL` is a *terrible* synonym for `loadeddata`.