Feature/mix cpu gpu op

Fix duplicate lr op after distribute transpiler

Speed/sequence expand

Fix Transformer Hang Problem

Add Wait() for reshape_op

Initialize large table value randomly

Refine double_buffer code

Multi stream thread pool

Split Executor.Run to Executor.Prepare and Executor.RunPreparedContext for inference

Fix warnings in sgd_op.h

Polish reshape op

fea/docker cudnn7

The fully connected: the operator is removed when the MKLDNN flag is OFF

* Fix CPPLint errors in operators

* Fix prior box op

* Fix Prior Box op

* Fix top_k_op.cu

* Fix pool mkmldnn

* Fix pool mkmldnn

update docker from cudnn5 -> cudnn7

Refine batch_norm_op.

Changing network configuration, avoid nan 

* 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