* add gflags for C++ unittest

Fix #6087

* add back print_operators_doc

* fix style check

* fix style check

* fix compile on cudnn7

* update

* update

* make silent

* Adding log loss operator

* Removing comments

* batch norm support matrix input

* update gpu code

* format code

* Make 'scale_op' supporting int and int64

* refine .cu file

* Add Python wrap of conv2d_transpose and its unittest

* Follow comments

* Fix format

* WIP send recv op

* WIP send recv

* put grpc impl in details

* put grpc impl in details

* update wip

* update proto

* update proto

* update proto

* clean cmake

* wip on op implementations

* wip on op implementations

* compile ok adding ut

* wip unitest

* add extern cares for linking

* wip add ut

* working version send recv

* revert optimizer.py

* update test cmake

* add libtool to dockerfile

* update cmake dependency

* update cmake depends

* update cmake grpc depends

* fix cmake dependency

* fix compile error

* fix compile

* follow comments

* update

* update copyfrom

* Refine CheckStyle Script

* Disable linkchecker for build_doc.sh

* Fix the latex comment syntax in sgd_op.cc

* Change \textunderscore to \_

* Complete shrink_rnn_memory_op comments

* Update