Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into feature/add_gather_and_BCast_op_handle

* init

* add some check

* add dist transpile logic

* add insert op for block

* init change get_pserver_program

* optimize code

* fix a bug

* can run now

* start to do table split

* start to process table gradient

* complete pserver part

* can send_vars now

* revert cpplint

* fix a bug

* optimize code

* move dist test to models

* revert the interface of distribute_transpiler.transpile

* fix prefetch_block

* optimize trainspiler code

* add comment to sum_op

* add warning log

* fix comment

* fix test_send_recv

* fix test_send_recv

* fix train with no distributed table

* optimize GetDims

* Eagerly drop local scope in iteration

* Correct create var

* Fix typo

* Debug

Update grpc version

* Add USE_OP of all operators and kernels and remove ARCHIVE_START/END in CMakeLists.txt of inference unittests.

* Remove ARCHIVE_START/END when linking inference shared library.

* Disable some fluid related cmake operations for cross-compiling.

 Make Average Model support for 'moving mean' and 'moving variance' of batch_normal op

make -j nproc when making inference_lib_dist

Improve test_parallel_executor.

* remove net op and cond_op

* fix cpplint

* fix dependency

* delete backward_test; fix compile

* disable batch_norm backward

* rm test_net.py

* make batchnorm test independent of backward.cc

* make test_layer_norm_op independent of backward.cc

* make test_layer_norm_op independent of backward.cc

* delete unused code

* clean up

* Fix cpplint errors, round2

* Fix pointer issue

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into feature/add_gather_and_BCast_op_handle

Disable unstable unittest

remove unused nccl.cmake

[Feature] Enable multi gpu distributed training of fluid

Fix api docs display error for fluid Initializer

 Add contents for manully build documentation(cn version)

* "add metrics"

* "add fluid metrics"

* "add import guards"

* "show warnings"

* "add demo"

* "fix ci"

* "add some details"

* "fix cci"

* "add demo Python"

* "add metrics"

Modify readers to fit the parallel executor

Make cuda_helper.h Pass cpplint