fix ArrowHelper so that it can deal with normals pointing down [0,-1,0] via creating a unit test (makeBasis).
optimization of ArrowHelper.setDirection suggested by @WestLangley
cleanup ArrowHelper GC usage, switch matrix->quat.
remove unnecessary Matrix4 unit tests.
reduce ArrowHelper axis check precision and improved formatting per @gero3
fix formatting per @WestLangley.
Merge remote-tracking branch 'bhouston/arrowhelper-fix' into dev
Cleaned up ArrowHelper code a bit.
Cleaned up Box3.
Removed ArrowHelper from SpotLightHelper.
I think it's a bit redundant.
Added .add(), .addColors(), .addScalar(), .multiply() and .multiplyScalar() to Color. Removed ArrowHelper from DirectionalLight too.
Updated builds.