Fix 3D Picking for Rays That Have a Zero Component

When using `MOAIPartition:propListForRay()` with a ray along the Z axis (i.e. (0, 0, -1)), there were false positives in the result buffer.

Fixed by checking against both `min` and `max` when the direction component is (almost) zero.

I also updated the 3d picking sample to check if it still works correctly.