* 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

* 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

* 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

update the margin rank loss api doc

* add pairwise distance cn docs

* fix link

* add alias

* refine format

* fix doc tree

* fix format

* add name

* change out -> output

* change eps -> epsilon

* fix name

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

* change cn.rst

* change cn.rst

* add api_cn

* test=develop

* add paddle.tensor

* add