* add cn doc of trace API

* add cn doc of functional ctc_loss and CTCLoss class.

* modified the format of doc.

* add en doc of ctc_loss and CTCLoss

* modified paddle.to_variable to paddle.to_tensor

* refine bceloss doc

* fix doc

* fix name

* fix api 2.0 directory migration

* add dir file and change x to input

* add doc of loss function binary_cross_entropy.

* delete static demo code.

* add 2/3d adaptive_pooling

* fix format

* fix format

* add en doc rst

* fix format

* fix doc

* fix doc

* refine example code

* unify example code

* Udpate the doc format for the paddle, test=develop

* polish some docs

* polish some docs

* Update square_cn.rst

* polish some docs

* polish some docs

* polish round docs

* polish round docs

* Update square_cn.rst

* polish some docs

* polish functional_cn.rst

* add mse_loss_cn doc

* add index

* add index

update the margin rank loss api doc

update demo code in NLLLoss_cn.rst

Update the docs of nn.loss.L1Loss and nn.functional.l1_loss

* add hapi Model, test=develop

* fix save inference model example, test=develop

* fix sample code, test=develop

* fix import, test=develop

* fix import, test=develop

* fix sample code, test=develop

* fix sample code, test=develop

* fix comments, test=develop

* change cn.rst

* change cn.rst

* add api_cn

* test=develop

* add paddle.tensor

* add

* http://newicafe.baidu.com/issue/DLTP-2069/show?from=page

* fixed one error of develop

* add 1.5.1 whl and fix some bugs (#1010)

* add windows install whl

* whl and bug

* fix some bugs

* update 1.5.1 cn API

* add url

* update api_cn; fix the error of reverting layers_cn to 1.4; include previous changes

* update layers_cn; add code example to elementwise_mod

* delete recordio_writer_cn; revert index_cn

* update api_cn after review

* fix io_cn.rst

* update layers_cn

* update io_cn

* recheck_structure&fix_typo

* fix_structure

* adjust_dist_structure

* fix_deadlink

* fix deadlink

* fix textual content

* fix issue #682 3 3.2

* fix issues in conv