fix bugs in fluid_benchmark

Refine prefetch

* wip

* use executor.complete to end trainer

* fix build

* fix build with distribute off

* fix typo

* fix cmake typo

* fix build

refine docs of elementwise_op etc.

* enable docstring checker and fix comments

* update

* update by comments

* fix build

* Add normalization operator.
1. Refine the raw norm_op and let it more general to support to normalize Tensor along any axis.
2. There is a bug in l2_normalize API, which lacks sqrt after `reduce_sum`.
3. Use norm_op to refine the l2_normalize API.
4. Fix bug in test_normalization_wrapper.py.

* Create dynamic_graph.md

* Update dynamic_graph.md

* Update dynamic_graph.md

* Update dynamic_graph.md

* follow comments, add graph

* Update dynamic_graph.md

* Update dynamic_graph.md

Build: add make before make install to catch up CMakeLists change.

* Add slice op.

* Remove using from header file and fix doc.

* Fix doc

* Small fix.

Make status update thread-safe

Enable CPU on Parallel executor

The status is updated in the Process() thread
and can be checked in another HandleRequest() thread.

* "add inplace attribute"

* "register inplace attribute"

* "change se-next model for memory-reuse"

* "fix typo"

* repick

* fix merge conflict

* "fix stupid error"

Fix fluid_benchmark stacked_dynamic_lstm model error

MKLDNN layout: Support for pool operator

replace use_event with use_cuda, because use_event means the program running with CUDA, so use_cuda maybe more intuitive.

Check SSA Graph

* 1. add weight decay feature into fluid benchmark test
2. add learning rate decay feature into fluid benchmark test
3. add L1&L2 regularization feature into fluid benchmark test
4. add error clipping feature into fluid benchmark test
5. add gradient clipping feature into fluid benchmark test

* Add some document to README.md under benchmark/fluid/ repo

* Add model_base.py

* Fix bugs in test_listen_and_serv_op

* 1. remove args out of fluid_benchmark.py
2. remove lr_decay, regularization, clipping out of fluid_benchmark.py

* add async_mode description to doc and remove the clipping description out

* for restart build

* to restart build

* remove optimization args from args.py

* 1. remove optimization from models
2. fix bug in test_listen_and_serv_op

* change the name retry_times to left_time

* change retry_times to the pserver start left time