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.

The engine library need to link paddle_pserver and paddle_network on linux.

Refine sequence max-pooling and add unit testing of gradient check.

Update docker_install_cn.rst fix nodebook to notebook

Add GRU Operator

fix nodebook to notebook

Fix type for unit test of huber_loss_op.

Bugs fix and expose sub_seq_layer.

add MKLDNNAddtoLayer

* Add GetFineGrainedLoDLength and AppendLoD

* Follow comments and fix bugs

* fix a compile error

* fix a compile bug

* 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