* Enable momentum operator for a ngraph engine
test=develop

* Update tests
test=develop

* Unnecessary line of the code as intended was removed
test=develop

* Refine cmake's download function.
test=develop

* Set DOWNLOAD_NO_EXTRACT to 1 pure download function.
test=develop

* Fix unpack problem in ExternalProject_Add, and it seem DOWNLOAD_NO_EXTRACT option is not support in cmake-3.5.
test=develop

* update fast install shell

* test=develop, enhance mac fast install

* fix pip Failure due to too low version;Add python virtualenv

* test=develop

* test=develop

* test=develop

* test=develop

* test=develop

* fix warnings

test=develop

* fix enforce test

test=develop

test=develop

test=develop

* Enable cross_entropy operator for a ngraph engine
test=develop

* Update tests
test=develop

* Added PADDLE_ENFORCE for the batch_norm operator
test=develop

* Update the message about which format are supported right now
test=develop

* Correct the comment in control_flow.py.

* Correct the argument list of ops.
test=develop

* Update API.spec.
test=develop

* Skip op_callstack attr for all op apis.
test=develop

* Remove use_mkldnn and is_test from python api.
test=develop

* Remove use_mkldnn and is_test from op_proto_maker and hard-coding them in python when generating doc string.
test=develop

test=release/1.3

test=release/1.3

* Add the CRFDecoding and LayerNorm's test case

test=develop

* Fix the size checking issue

test=develop

* Remove the remnant code

test=develop

* Add TestAllImpls and double support

test=develop

* Clean Code

test=develop

* Add benchmark test for LayerNorm & CRFDecoding

test=develop

test=develop

test=develop

test=develop

* inplace group

* test=develop

* fix && test=develop

* fix && test=develop

* test=develop

* Fix debug mode in prior_box_op
* Refine code

test=develop

test=develop