* Chage `IndicateDataType` to `GetKernelType`. Make it easier to
  understand.
* Change `OpKernelKey` to `OpKernelType`
* Make operator developers can customize which kernel the operator will
  use in runtime.

* Compare Operator

* Follow comments

Fix ci not exit 1 when error

* small fix

* fix comment

* address comment

* small fix

Fix cmake error when building with WITH_AVX=OFF.

Refine get cuda context

MemoryHandle* --> MemoryHandlePtr

* Use stable_sort in lod_rank_table

It is easy to debug and test when use `stable_sort`and the time
complexity is not changed.

* Add LoDTensorArray

* Stash

* Better debug message for IsInitialized

* Stash

* Better debug message for IsInitialized

* Complete array read/write op unittests

* Add unittest, Gradient of array read/write

* Follow comments

* "fix unsigned compare problem"

* "remove gtest from CMakeList"

* "remove namespace"

Please refer to https://github.com/PaddlePaddle/Paddle/issues/5363

An important change on lod tensor indexing. A higher level offset will be based on its next level rather than an absolute offset.

This changed was accidently reverted in a previous pull request.  This pull request adds back in the print_operators_doc to the docker image.

Discussed with Helin and Yi. Currently we have a binary "print_operators_doc" that is built that generates a JSON document. This JSON represents the API documentation of paddle, and will be used by PaddlePaddle.org to generate API documentation.

This issue is to request "print_operators_doc" to be added to the production paddlepaddle/paddle:latest image.

* Use stable_sort in lod_rank_table

It is easy to debug and test when use `stable_sort`and the time
complexity is not changed.

* Add LoDTensorArray

* Stash

* Better debug message for IsInitialized

* Stash

* Better debug message for IsInitialized

* Complete array read/write op unittests

Add 3D Convolution operator implemented by GEMM.

Pnp evaluator

Add 3D convolution transposed operator.

Rename doc/howto/cross_compiling into doc/mobile

fix bugs of softmax_with_cross_entropy op.

Put files to platlib

Fix the doc for Momentum and Adam optimizer.