Enhancement: Add an option in video scenes to avoid loop.

[AndreVianna]

The title is self-explanatory.
But the idea is the have video scenes as cut scenes that allow a video to be played once.

With AI we can easily create animated cut scenes with voice over that create awesome experience to the players.

But once you move the players to the scene each player may see the scene in a different moment because of slower network or slower machines.

Play the video just once would be enough to ensure they see the cut-scene and it stop at the end to the video.

Just a check box that would be enabled when video background is selected.

Not present in version v1.27.

UI changes:

1. add a check box that is only visible if the "link a video" option is selected with label "play only once" or "no loop".

Code:
In the HTML canvas the only change is to toggle the "loop" property of the video tag.

So the checkbox would only control is the property is present or not.