* Add env value to  log to stdout; 2.Add logger name

* Optimize log messages in dygraph-to-static

* Replace logging.warn and warnings.warn with logging_utils.warn

* Add naming rule if not specific InputSpec.name

* fix function name typo

* refine comment

* remove print statement

* Fix Python Version compatibility

* add import six

* add InputSpec

* add unittest for tensorSpec and SimpleNet