CPP support for region and reorg operators (#1115)

topi/include/topi/cuda/vision.h

topi/include/topi/rocm/vision.h

topi/include/topi/vision/reorg.h

topi/include/topi/vision/yolo2/region.h

topi/python/topi/cpp.py

topi/python/topi/cuda/__init__.py

topi/python/topi/cuda/vision.py

topi/python/topi/generic/vision.py

topi/python/topi/rocm/vision.py

topi/python/topi/vision/reorg.py

topi/python/topi/vision/yolo2/region.py

topi/src/topi.cc

topi/tests/python/test_topi_region.py

topi/tests/python/test_topi_reorg.py

topi/tests/python_cpp/test_topi_region.py

topi/tests/python_cpp/test_topi_reorg.py