New-style API and minor fixes -> v1.0.1

Hi Daniel,

In response to your mail, here are some updates to the media player. The biggest change is that I converted the GUI to the new-style plug-in API, as described here:

- <http://osdoc.cogsci.nl/plug-ins/create/>

This shouldn't make any functional difference, but it's a bit cleaner.

I also caught one bug (#89c937f) and noticed something odd: Key presses are sometimes ignored, seemingly when the focus is on the video window. First clicking the window frame and then pressing a key does work. The issue doesn't arise in fullscreen mode, and could very well be Linux specific. So I wouldn't worry about it too much, but just fyi.

Cheers,
Sebastiaan