* polish infer shape registry, test=develop

* modify some operators registry, test=develop

* add_dygraph_execution_context

* add dygraph infershape context and execution context; test=develop

* fix imperative bug; test=develop

* remove inputs outputs interface from execution context,
because it have same function with inputNames;
test=develop

* remove tracer_test ctest; test=develop

* fix split op bug; test=develop

* fix unitests bug; test=develop

* fix distribute test bug; test=develop

* fix ngraph compile bug; test=develop

* fix grad maker bug; test=develop

* fix load op bugs; test=develop

* fix operator.cc construct bug; test=develop

* remove useless name find in operator; test=develop

* add tracer_test; test=develop

* fix concat, split bug; test=develop

* remove tracer_test unitest; test=develop

* fix attribute check bug; test=develop

* add test code to fix converage; test=develop

* remove useless code, change check backward input in engin; test=develop

* unlock var type infer shape;test=develop

* add ShareAllLoD api; test=develop

* add dygraph infershape context unitest; test=develop

* remove increase and decrease lod in dygraph; test=develop

* addd override; test=develop

* fix increase descrease lod; test=develop

* fix paddle_enforce; test=develop

* disable lod op dygraph check; test=develop

* fix paddle enforce error; test=develop

* add comment for op_registry and OperatorBase; test=develop

* optimize the comment of op_registry; test=develop

* fix format of comment; test=develop

* fix format of comment; test=develop

* optimize the format of comment; test=develop

* optimize the format of the comment; test=develop

* optimize comment of op_registry; test=develop

* update ngraph ops test=develop

* update unittest test=develop

* increase coverage test=develop

test=develop

* update for multiple threading
test=develop

* remove PADDLE_ENFORCE test=develop

test=develop

* upgrade ngraph to v0.24 test=develop

* simplify io test=develop

* Enable ngraph layer_norm operator

test=develop

* Disable/Enable cuda, new unit-test test=develop

* Fix use_cudnn test=develop

* Fixed test_layer test, new funciton is added test=develop

* set use_cudnn by default test=develop

* delay infershape test=develop

* fall back subblock to paddle test=develop

* fix edge cases test=develop

* remove output duplicates test=develop

* handle reshape2_grad infershape test=develop

* Enable elementwise_div operator test=develop

* Fix update date test=develop

test=develop

* Enable less_than ngraph operator

test=develop

* Added compare unit-tests test=develop

* Update: date && removed import test=develop

test=develop

* add depthwise_conv2d test=develop

* use cpu for ngraph test=develop

This reverts commit f34830e2.

* Enable sqrt operator for the nGraph Bridge.

test=develop

* Update activation_op.h

test=develop

test=develop

*  Enable assign operator for a ngraph, test=develop

* Cross_entropy operators needs to be updated

test=develop

* add increment op to ngraph engine

test=develop

* fix style errors

test=develop