Improve # of objects rendered

[typpo]

I'm at ~40fps on my 11 inch macbook air @ 5000 objects. Desktop computer can go up to 50,000 fairly smoothly.

Thoughts on improving rendering capabilities:

• There is still some old CPU rendering/movement code. This should be removed.
• Group objects with similar orbits and treat them the same. If inclination, eccentricity, and semimajor axis are within a few percent of one another, should be good enough for the purposes of the simulation.
• Cache positions? This didn't help in the past, but now that rendering methods changed it may be worth it in some capacity.