* fix nccl version

* enable nccl test

* compile with nccl2

* add ncclGroup; it is necessary in nccl2

* add back libnccl-dev

* refine inference_lib_dist after code move, and add it to docker/build.sh

* remove is_directory in inference_lib.cmake

* add back print_operators_doc

* fix style check

* fix style check

Use CUDA_ARCH_NAME=All in the paddle/scripts/docker/build.sh and remove 20 21(20) in cmake/cuda.cmake.

This changed was accidently reverted in a previous pull request.  This pull request adds back in the print_operators_doc to the docker image.

Discussed with Helin and Yi. Currently we have a binary "print_operators_doc" that is built that generates a JSON document. This JSON represents the API documentation of paddle, and will be used by PaddlePaddle.org to generate API documentation.

This issue is to request "print_operators_doc" to be added to the production paddlepaddle/paddle:latest image.

After discussion with Helin and Yi, this change adds "print_operators_doc" executable to the Paddle docker nightly image.  This docker image will be pulled by PaddlePaddle.org nightly job and will generate the operator documentation to be put on PaddlePaddle.org website.

* init add

* add topk op

* someupdate

* fix style check

* add test py file

* update top k cuda kernel

* follow comments

* remove debug print

* fix casting error

* fix casting error

* fix casting error

* fix rename bug...

* fix travis