Reducing part complexity

[Travis Cobbs]

When LDView does primitive substitution, the lowest quality setting does in fact do this for all circular primitives, reducing them to match an 8-sided circle instead of the standard 16-sided circle. I had forgotten about that. You can't really go below 8-sided with generic LDraw primitives without introducing problems. (And obviously, the x-16 primitives can't even go down to 8.)