VDPAU breaks on certain video clips

Disabled VDPAU on all producers in the XML OpenShot file. This is to prevent issues related to vdpau. Many reports have been submitted to me where vdpau is breaking a video clip, which is why I am disabling it.

VDPAU is not as effective in video editing, as opposed to video playback. It does help lower the CPU, but it only helps a little bit. So, disabling this gives us much greater stability, and a little worse CPU. I think it's a good trade off (for now).