`loadTextureCube` takes into account `onError`

OrthographicTrackballControls updates

THREE.Line offsets fix

Fixed non-indexed line arrays not using offset start index. Also removed needless variable assignment from THREE.Line case and THREE.PointCloud case.

THREE.PointCloud offsets fix

Fixed offset particle drawing always starting at 0 index. Looks like it was copy'n'paste typo.

Fix StereoEffect so it actually clips correctly

Line and point rasterization is not clipped by gl.viewport,
gl.viewport only clips vertex calculations. If a vertex is
on the edge of the viewport (so it's not clipped) but it's
being turned into a `POINT`, and say `gl_PointSize = 16` then
 that point will get rendered partially outside the viewport.

Also gl.clear is not affected by viewport settings, only scissor
settings so there's no reason to change the viewport to clear.

Object3D docs: Remove deprecated properties

And add default & readonly information.

Fixed missing line break in documentation

onLoad -- callback function doesn't appear on a new line. Added a </br> at the end of the previous line to make onLoad appear on a new line. This cleans up the formatting.