* Add the argmax, argmin api doc for the api 2.0, test=develop

* add uniform op doc

* fix uniform en format

* delete useless code

* test distribution doc

* add paddle.rst

* fix paddle.rst

* Add distribution_cn

* Fixed doc in cn

* fix cn doc

* test paddle_cn

* Distributin, temp fix of Normal and Uniform

* fix code doc

* test_broadcast

* optimize doc

* return to the original index_cn.rst

* hidden _to_variable func

* refine sign tanh api, test=develop

* Add Tanh, test=develop

* fix en, test=develop

* test=develop, add addmm doc

* add addmm doc

* test=develop, add addmm doc

* test=develop, add pad doc

* restore addmm

* test=develop, add pad

* test=develop, fix pad interface

* test=develop, add pad eng doc link

* test=develop, add other pads

* test=develop, remove pad default

* test=develop, fix const pad1d code

* test=develop, fix var

* test=develop, fix pad typo

* test=develop, rename tovar to totensor

* test=develop, fix code

* test=develop, fix typo

* test=develop, fix cos_sim interface

* test=develop, fix typo

* 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

* rename the inputs and update code example, test=develop

* update doc

* add mse_loss_cn doc

* add index

* add index

* test add api

* add_api test=develop

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 the max, min, maximum, minimum api for the paddle 2.0

update the api doc for the cumsum op 

update the sort api, delete the unused index output

* Add fluid.rst

* fix cn rst

 Fix the compare ops doc for the api2.0

Fix the argsort, sort the api doc for paddle2.0

fix cross op doc for API2.0