Split input objects into multiple .vox files when maximum size is exceeded.

[david-rhodes]

It would be useful to automatically segment a physically large input into several (max 2016^3) vox files so that the conversion does not simply fail, and will allow the creation of highly detailed voxel objects. Obviously this couldn't be loaded simultaneously into MagicaVoxel, but at least you could compose scenes in other tools (Unity, Unreal, etc.).