Move videos off the main Qt thread.

[Mysticial]

Right now, the video widget and rendering appear to be on the main UI thread. This is problematic if there are multiple videos or on slow computers.

I've tried in the past to move it to a different thread, but Qt does not like anything UI to be off the UI thread.

See if there is a way to do this. There's no "real" reason for all the videos to be on one thread.