Implement realtime clutter #14
Description
In the old VoxelMetric, clutter was hard-coded in the voxel world. Sometimes, this might be desirable, however, in general, it is not. Clutter should be generated around the camera in real-time rather than being a property of chunks. Having it this way would help save some memory (simpler voxel chunks) and even performance (no need to rebuild chunk when clutter changes).