v0.5.1

• v0.5 documentation updates
• Nonlinear functionals and modules
• Warning when using cuda without ME cuda support
• diagnostics test
• TensorField slice
  • Cache the unique map and inverse map pair in the coordinate manager
  • generate inverse_mapping on the fly
• CoordinateManager
  • field_to_sparse_insert_and_map
  • exists_field_to_sparse
  • get_field_to_sparse_map
  • fix kernel_map with empty coordinate maps
• CoordiateFieldMap
  • quantize_coordinates
• TensorField binary ops fix
• MinkowskiSyncBatchNorm
  • Support tfield
  • convert sync batchnorm updates
• TensorField to sparse with coordinate map key
• Sparse matrix multiplication
  • force contiguous matrix
• Fix AveragePooling cudaErrorMisalignedAddress error for CUDA 10 (#246)