Ploids - A Boid Simulator

A pretty standard implementation of Boids, but with a focus on how it might be useful in a multidirectional shmup.

LMB:  Attract Ploids
RMB:  Repel Ploids
Mouse Wheel:  Zoom In/Out
MMB:  Reset Zoom
Arrows:  Pan view.

Hold SHIFT:  Pan and Zoom faster.

I'd like to build this out to have all the behaviors discussed in the famous GDC talk : https://www.red3d.com/cwr/steer/gdc99/

I noticed that in this paper Boids are meant to have an Angle associated with their "Neighborhood" of perception, mine don't do that.  I might do that next.