Use line segments instead of circles for collision detection

[JeremyLeland]

The difference between bounding circle and actual ship outline is more obvious with larger and more complicated ships. Bullets end and throw sparks in the space to the side of ships. This would look better if we used several segments that more closely approximate the ship/rock shape.

Bounding circles should still be fine for avoidance.

[JeremyLeland]

We do this with BoundingLines now