Fixes to delete voxel and color/add voxel to allow for unwinding color reaveraging

- Change VoxelTree::deleteVoxelCodeFromTree() to do all in place recursion so that on unwinding we can do tasks like marking the path as changed and handle color re-averaging.
- Change VoxelTree::readCodeColorBufferToTree() to do all in place recursion so that on unwinding we can do tasks like marking the path as changed and handle color re-averaging.