* set default dtype for distribution API

* Add unittest

* Add unittest

* fix import get_default_dtype problem

* delete change under fluid.layers.nn

* little change

* upload code for tensor.rand

* fix import

* update example, change paddle.tensor.rand to paddle.rand

* change 'variable' to 'Variable',  test=develop

change 'variable' to 'Variable' in description,  test=develop

* add pre-commit check

* add pre-commit check

* pre-commit check, test=develop

* add more unittest code

* trigger ci, test=develop

* pre-commit check, test=develop

* update api and test comment, test=develop

* update api and test comment, test=develop

* add more type check, test=develop

* add detail error info for device, test=develop

* add unnittest, test=develop

* resolve conflict and pre-commit check, test=develop