* test=develop, reconstruct layer helper to fit imperative usage

* test=develop, fix import error on py35

* test=develop, fix rnn gradient error

* test=develop, delete test use code

* test=develop, remove helper from imperative usage

* test=develop, fix test_base_layer using new helper

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, reconstruct layerhelper for imperative mode

* test=develop, fix bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix test failed bug

* test=develop, fix bug

* test=develop, polish code

* remove the ignored from is_empty and less_than test=develop

* fix api spec test=develop

* fix the api spec test=develop

* test=develop

* unified PE and compiler
test=develop

* Polish code
test=develop

* add ir memory optimize test case for IfElse op, test=develop

* fix some unitttest failure by force using the python memory_optimize, test=develop

* tweak comments, test=develop

* fix unittest, test=develop

* fix unittest, test=develop

test=develop

* MKLDNN: Add UT for conv_transpose_mkldnn op.
test=develop

* MKLDNN: Add fuse_bias check UT for conv_transpose_mkldnn op.
test=develop

test=develop

* Unified ParallelExecutor and Compiler

test=develop

test=develop

* fix image_resize annotation

test=develop

* fix some typo

* Update nn.py

* Update interpolate_op.cc

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

* staged.

* polish code

* polish code. test=develop

* polish code. test=develop

* api change. test=develop

* fix default value. test=develop

* fix default value. test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop