* update doc, test=document_fix

* add attr(dtype)

* refine code

* add unique_v2 op

* remove unique_v2 op

* update doc

Those ops include，scale， sum， sums，unique_with_counts，unique，
wherre， add error message and test case

* fix the device supported of the op unique and unique_with_counts.
test=develop
test=document_fix

* Fix the precision of test in the op of unique and unique_with_counts.
test=develop
test=document_fix