remove unused doc folder

* Simplify the compare op for CPU.

* Use asynchronous tensor copy in reshape_op's kernel.

* Optimize while_op for test, avoiding creating variables every time.
test=develop

* Enable the cache of kernel type and kernel function.
test=develop

* Enable profiling with gperftools.

* Remove flags for testing, and fix the linking error.
test=develop

* Delete the codes of ChooseKernel.
test=develop

* Fix bug when preparing ExecutorPrepareContext for while_op.

* Fix missing depending on grpc libraries.

* Remove the redundant print.
test=develop

* Follow comments.

* Remove the codes related to prepare the ExecutorPrepareContext for while_op.
test=develop

Enable element_wise_add operator for a ngraph engine

Enable softmax operator for a ngraph engine

test=develop

add imperative mode design

Enhance key generation for Pool INT8 test

Fuse/second order mul sub and fuse repeated fc relu

* disable conv3d mkldnn in dam

* Add some comments  test=develop

expose CompiledProgram

fix deadlink in CONTRIBUTING.md

polish imperative codes

adam support multithread

test=develop

test=develop

test=develop

* fix github issue 15267 test=develop

* fix github issue 15267 test=develop

add the python callstack for debug support test=develop

test=develop

test=develop

test=develop

fix imperative compile when WITH_PYTHON=OFF

convert all tests to new CompiledProgram API

test=develop

test=develop

fix multi-threads in ZeroCopyProfile

test=develop

test=develop

test=develop

* open fetch_feed_op test
test=develop

* code refine
test=develop

* reset timeout for test_parallel_executor_fetch_feed
test=develop

* disable test_parallel_executor_fetch_feed for windows
test=develop

* refine unit test
test=develop

Fix expand op compile time bug

test=develop

test=develop