Space-effect parallax in camera GUIs

[thesixthroc]

When empty space tiles (or others with `effect = "space"`) are viewed through a camera GUI, the parallax effect of the stars accounts for the zoom of the viewing player. If my understanding is correct, the position for parallax is taken as the position of the camera GUI on the screen.

For certain intended effects, it would look much better if the viewing player's position was used to set the parallax, even if that player is on a different surface. I would like a modding interface on the camera (or tile) which is a single boolean to toggle this behavior.