Copy and Paste Voxels

New edit tools added for voxels...
- Copy & Paste
- Export & Import
- Eyedropper
- while in select mode, delete/backspace will delete the selected voxel. Allows you to quickly delete while in select mode

New shared utility functions added for:
- cherry picking sections of an octcode
- rebasing an octcode
- chopping an octcode

New features added to VoxelTree:
- ability to chop and rebase during encoding and decoding

Bug Fixes:
- Fixes delete voxel of last child voxel of previously created larger voxel