Add `lod_array_length` operator

remove unused INTEL_MKL_ROOT etc.

fix typo

Enable hidden/cell state initialization and enhance unit testing in LSTM operator.

Bug fix for ScaleSubRegionLayer

NCE does not need to set its activation.

Update annotations of layers.py.

Add ScaleSubRegion Layer.

add clip_by_norm op

update tags of MKLML and MKL-DNN

* Add LoDRankTable

LoD Rank Table stores the `level` of `lod` which is ordered by sequence
length in descending order. It is useful when implement dynamic RNN and
is shared by dynamic RNN memory, dynamic RNN slice input and dynamic
RNN slice output operators.

* Add skeleton for array_to_lod_tensor and lod_tensor_to_array

* Add VarType::LoDTensorArray

* Add PyBind of LoDTensorArray

* Add InferVarType

* Add first unittest

* Add ut

* Add unittest

* Add unittest

* Add unittests

* update

* init

* add infershape for lod_tensor_to_array_op

* compelete array_to_lod_tensor_op

* copy data

* clean code

* clean code

* Fix unittest data

* fix bugs

* fix compile error

* Refine TensorToArrayOp

* refactor array_to_lod_tensor

* Unittest

* fix bugs

* Fix unittest

* Fix unittest

* debug

* Debug

* Fix unittest

* Add grad for ops

* Debug

* Fix a bug

* fix a bug

* fix a bug

Add force_cpu for fill_constant op

CompareOp's kernel device type is decided by input tensor place

Feature/shrink memory op

and abandoned deprecated sum API interface

add doc for image.py

fix accuracy cudamemset