Balance parameter_opt between cards

matmul support float16/double

Parallel Executor revised feeder

* Update the mnist test cases with the new API syntax.

* Turn on the tests for MNIST

* delete the test files got merged accidently.

* Enable the mnist tests. ready for test driven development.

* Comment out the infer first
This is to confirm that the Trainer.train is working

* Add CMake file to include the tests

* Make the train program only return avg_cost for now

* Update the tests to use the latest syntax

typo fixed

* add Inference.infer

* optimize code

* update no_test_word2vec_new_api.py

* update trainer

* split check_and_get_place

* use inference_program to save inference model in Trainer

* update demo

* update save_inference_model

* clean code

update mklml version, disable building tests and examples when install mkldnn

fix unittest-error: test_network_with_dtype

Fix two deadlinks in paddle/README.md

Fix compile on mac

Clean OpProtoAndCheckerMaker

disable building tests and examples when install mkldnn
skip -Werror=unused-result

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into feature/matmul_support_float16_double

* a draft of trainer.test()

* polish trainer.test()

* polish trainer.test()

* update code format

* update

* polish code

* polish code

* polish code

* Make trainer.test follow the rule of returning [loss, metric, metric, ..]

* Add FP16 option in save_combine_op

* Fix casting issue

Clean Parallel exe