Make the height value of display entities cull box work like width.

Currently, the way the cull box setting for display entities work is by setting a width and a height. The width value defines the maximum width of the entity, but height defines the maximum height of the entity from the y-value of the actual entity itself. This means that no matter what you input for the height, if the display entity's core is in the center of it, the bottom half of the display will be out of the cull box region and thus not render when the camera is looking toward the bottom of the model.