Collision Detection & QuadTree

Demo video: https://crayz.tv/files/sharex/2018-05-28%2017-19-29.mp4

A simple collision detection system. Includes two algorithms:

• Brute checks all bodies against all other bodies, and it can be hard on performance and only recommended for 100 or less bodies.
• QuadTree queries a QuadTree to test collisions against nearby bodies only. Much more performant than Brute, but takes a bit of extra work to set up.