* 1. implement StopAll in ListenAndServOp
2. make pserver receive the SIGINT and SIGTERM from outside
3. add unittests for listen_and_serv_op in python

* 1. add blocking queue set to record queue
2. aware all blocking queue when exit and exit gracefully

* 1. Remove comment lines from blocking_queue.h
2. Implement SignalHandler and move all global vars and funcs into it

* 1. Make code follows the style check
2. Move the SignalHandler out of the unnamed namespace

* 1. Make yapf happy

* 1. Call Stop() in destructor to release the resource allocated by ListendAndServOp
2. Change exit status to EXIT_SUCCESS after handling the signal from outside
3. Remove the mis-usage of REMOVE_ITEM in unittests

* 1. use DISABLE_COPY_AND_ASSIGN
2. use program once macro only

* Add quad transform.

* Fix some syntax error.

* Fix CUDA kernel launch configure.

* Generalize geometry channels.

* Rename QuadTransform to PolygonRestore.

* Rename op.

* Rename op and fix computation.

* Modify CMakeLists.txt for box_restore op.

* Refine code:
1. rename op
2. uncomment unitest on GPU

* unify UpsamplingBilinear2d interface specification

* unify UpsamplingBilinear2d interface specification

* fix name conventions

* small fix about computation order

* Expose bilinear operator into Python API

* delete unused lines

* delete unused lines

* fix typos

* fix name arg and typos

* Enhance reduce op for multi dims.

* Uncomment some unitest.

* Uncomment unitest.

* Remove unused code.

* Fix infershape and python wrapper.

* Add more examples.

* Fix l2_normalize.

* Fix normalization_wrapper.

* Polish code.
1. Rename unitest function.
2. Rename const variable.

1. If all bboxes are not difficult ground truth, the users can not define the data layer for this flag and not the input can be None for detection_map API.
2. Set default value for aspect_ratios in prior_box API.
3. Add more check in prior_box API.

* Added kernel to is_empty_op

* Added python API

* Updated code as required

* Updated unittests

* listen_and_serv use localscope

* fix ut

* "fix ci"

* "fix network config"

* "rerun ci"

Change default split minimize value to speed up transport data to pserver

* add dist transpiler unit test

* update by comment

* update by comment

* fix ci

* fix ci