* 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

* 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

* Update `no_grad` docs

add alias `paddle.no_grad`
use `paddle.no_grad()` for decorator usage
update code sample

* Fix alias

* Reword decorator usage note

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