Broken orbit rendering

[petronius]

Orbit.from_true_anomaly() will return a v_position with a flipped sign on the y axis in many cases. This likely due to calculating the eccentric anomaly from arctan() (and not arctan2, thus the angle ending up in the wrong quadrant), but I am not sure.

This is only a problem with the orbit plotting code, though, and doesn't affect actual spaceship movement.

[petronius]

Could also be related to the rendering of the orbit. Under certain cases broken orbits appear to rotate the camera when the focus isn't on the origin.