* add fluid.embedding cn doc test=document_preview

* fix example code test=document_preview

* refine ref link

* fix param True style

* add fluid.one_hot zh doc

* refine code style

* fix dtype description

* add one_hot_cn.rst in fluid_cn

* add default value

* support LoDTensor

* modify embedding doc

* refine param_attr

* rm warning

* fix data

* add padding data update doc

* add np.dtype