Add python training implementation

pbnr_pytorch/.gitignore

pbnr_pytorch/diff_rasterization/bitmask.cuh

pbnr_pytorch/diff_rasterization/ext.cpp

pbnr_pytorch/diff_rasterization/rasterization_utils.cuh

pbnr_pytorch/diff_rasterization/rasterize_points.cu

pbnr_pytorch/diff_rasterization/rasterize_points.h

pbnr_pytorch/diff_rasterization/rasterize_points.py

pbnr_pytorch/diff_rasterization/rasterizer.py

pbnr_pytorch/diff_rasterization/setup.py

pbnr_pytorch/diff_rasterization/soft_depth_test.cu

pbnr_pytorch/diff_rasterization/soft_depth_test.h

pbnr_pytorch/diff_rasterization/soft_depth_test.py

pbnr_pytorch/lpips_pytorch/__init__.py

pbnr_pytorch/lpips_pytorch/modules/lpips.py

pbnr_pytorch/lpips_pytorch/modules/networks.py

pbnr_pytorch/lpips_pytorch/modules/utils.py

pbnr_pytorch/measure_leave_one_out.py

pbnr_pytorch/model_defs/Loss_Functions.py

pbnr_pytorch/model_defs/ResNet_2DConv.py

pbnr_pytorch/model_defs/netblocs.py