HedgeEdit - Sorting/Drawing scenes

[Radfordhound]

Obviously we need some code in-place to draw stuff to the screen lol.
Just drawing a cube with a basic unlit shader, for example, is easy. The tricky part is coming up with a draw loop that will also scale well for when Forces shader support is implemented.

I need to write code to:

• Sort objects for best drawing performance
• Sort objects for proper transparency (back-to-front)
• Draw objects in proper order