v0.5.2

• spmm average cuda function
• SparseTensor list operators (cat, mean, sum, var)
• MinkowskiStack containers
• Replace all at::cuda::getCurrentCUDASparseHandle with custom getCurrentCUDASparseHandle (issue #308)
• fix coordinate manager kernel map python function
• direct max pool
  • SparseTensorQuantizationMode.MAX_POOL
• TensorField global max pool
  • origin field
  • origin field map
  • MinkowskiGlobalMaxPool CPU/GPU updates for a field input
• SparseTensor.dense() raises a value error when a coordinate is negative rather than subtracting the minimum coordinate from a sparse tensor. (issue #316)
• Added to_sparse() that removes zeros. (issue #317)
  • Previous to_sparse() was renamed to to_sparse_all()
  • MinkowskiToSparseTensor takes an optional remove_zeros boolean argument.
• Fix global max pool with batch size 1
• Use separate memory chunks for in, out map, and kernel indices for gpu_kernel_map for gpu memory misaligned error