Do not use the api method as fallback

Because when the ie method fails, the api method also fails.
But embedding works always.
Add link to addon settings at the bottom of the size menu
Fix for only the gui but not the video being resized

We need to continually check the size, because it my change when the user enters
or leaves fullscreen. We use the timeupdate event of the video for this. This is
not perfect but at least only runs when the video is actually playing.
Add option to specify the video quality manually or automatically
Add workaround for youtube volume bug

It simply sets the volume to 100% before the video starts
Scale annotations, because they are not scaled automatically

The scale calculation as for now is probably very fragile and will break sooner or
later. But as annotations are not that important, this seems bearable.
Fix video positioning for non-16:9 videos
Fix videos not playing on playlists

The IE method does not seem to work on playlist sites. (It does not work in a real
IE eather) So we use the fallback of embedding here.
Emulate playlist autoplay for included iframes

Because youtube cannot handle the autoplay for playlists anymore if we replace
the internal player with the iframe, we have to listen for stateChange event in
the ifram ourselves and react accordingly.
This currently uses the UI and not the API for playlist control, but could be
easily adapted.