Optimized SAT.collides method by precomputing vertex projections

[bchevalier]

Changes

• Added a Projection Component.
• Added a projections property onto bodies that contains the projections of all the body's vertices onto its own axes.
• Modified Sat._overlapAxes method in order to benefit from the precomputed projections.

Includes #555

Result

• More lines of codes due to additional Projections component.
• Roughly 40% performance gain on the SAT.collides method.
• From 50% to 200% performance loss on the Body.update method.
  N.B the speed-up of the SAT.collides method far outweighs the performance loss of the Body.update method.

Circle Stack: engine performance gain 29.3% (=1.4x)

Before

After

Mixed Shapes: engine performance gain 24.3% (=1.3x)

Before

After