Show framerate, not just frame number
Limit planets for a system to 4 max

Having issues rendering them past that point.
Hopefully make this comment more clear
Limit rotation_angle around the star to -pi/4, pi/4

Doing this so the planets don't all look weird. I'd like to have a better way
of determining this for all of the planets together in the system, but that
might need to wait until I study some better ways of modeling systems and
the dynamics involved in creating one from, say, a dust cloud.
Make these labels look better

Need to move this sidebar view nonsense into a separate view outside of
this controller.