- ngarph: elementwise_sub, elementwise_mul
- mkldnn: transpose, sum
- others: scatter_nd

test=develop

* fix PythonAPI test in Op unittest, test=develop
* fix unit tests that do not need to inherit OpTest, test=develop

* add scatter_nd op, test=document_preview test=develop

* fixed the document, test=document_preview test=develop

* modify the notes, test=document_preview test=develop

* remove the ShareDataWith, test=develop