GitLab

Removed debug.

Now we can have more than one media loaded...

This also fix the crash when clicking on play without any media loaded

Removed debug

YOUHOU, FIRST CODE COMMIT, YAY SACRIFICE PONIES!
(Don't be afraid, I love ponies, it's a friendly sacrifice)

Added some doc

You can now play/pause the render preview

w00ps, my bad, forgot this earlier :)

Removed useless Track.cpp/h

... and render is stopped when there is nothing more to do

This way, the TrackWorkflow can return a black output when nothing has
to be rendered

However, they must NOT be simultaneous (for now !)