Merge pull request #2698 from soltanmm/reorganize-python

src/python/grpcio/.gitignore

src/python/grpcio/MANIFEST.in

src/python/grpcio/README.rst

src/python/grpcio/commands.py

src/python/grpcio/grpc/__init__.py

src/python/grpcio/grpc/_adapter/.gitignore

src/python/grpcio/grpc/_adapter/__init__.py

src/python/grpcio/grpc/_adapter/_c/module.c

src/python/grpcio/grpc/_adapter/_c/types.c

src/python/grpcio/grpc/_adapter/_c/types.h

src/python/grpcio/grpc/_adapter/_c/types/call.c

src/python/grpcio/grpc/_adapter/_c/types/channel.c

...python/grpcio/grpc/_adapter/_c/types/client_credentials.c

src/python/grpcio/grpc/_adapter/_c/types/completion_queue.c

src/python/grpcio/grpc/_adapter/_c/types/server.c

...python/grpcio/grpc/_adapter/_c/types/server_credentials.c

src/python/grpcio/grpc/_adapter/_c/utility.c

src/python/grpcio/grpc/_adapter/_common.py

src/python/grpcio/grpc/_adapter/_intermediary_low.py

src/python/grpcio/grpc/_adapter/_low.py