* add docs

 update the doc for the topK

* add unique doc

* Test SmoothL1Loss

* fix SmoothL1Loss doc

* fix some error

* fix to_tensor and add name=None,test=develop

* add bernoulli

* refine manual_seed

* add bernoulli

* refine bernoulli

* refine squeeze

* refine unsqueeze

* refine stack

* fix manual_seed

* fix manual_seed

* add cn doc of dropout series

* fix doc in quto and details

* fix doc of AlphaDropout

* fix cn doc details

* refine doc of functional dropout

* refine details in cn doc

* refine order

* fix sample code in Dropout2D/3D

* add cross_entropy_loss_cn doc to functional_cn and loss_cn

* fix bug in doc/fluid/api_cn/nn_cn/functional_cn/cross_entropy_loss_cn.rst

* fix format for functional_cn/cross_entropy_loss_cn.rst and loss_cn/CrossEntropyLoss_cn.rst

* Add chinese and english documents of paddle.prod

test=develop

* 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

 add doc of isnan, isinf, isfinite

* 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

* modify the doc, test=develop

* 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.

* Update `paddle.clamp` doc

rename to `paddle.clip`
`input` -> `x`
remove `out`
update samples
wording: `Variable` - > `Tensor`

* Apply template

* Update `enable_imperative` -> `disable_static`

* Update sample: `to_tensor`

* modify the doc, test=develop