[MXNET-40]add multi proposal operator (cpu version) and fix the bug i…

…n proposal op (gpu version) (apache#9939)

* add multi proposal operator (cpu version)

* lint fixed

* add the unit-test for MultiProposal Operator

* fix PrepareOutput bug in proposal op(gpu) and multi_proposal op(gpu)

* fix _nms function in the GPU implementation of Proposal and MultiProposal

* use openmp to optimize MultiProposal Operator

* fix MultiProposal Building on Windows

* rm openmp collapse token in MultiProposal.cc

* use signed iterator for MultiProposal

* add cpu/gpu consistency test for Proposal and MultiProposal

* fix test samples in test_multi_proposal_op

* add USE_STABLE_SORT_PROPOSAL=1 for Jenkinsfile

* use stable sort for MultiProposal and change Building Settings back

* skip the cpu/gpu consistency test for Proposal Operator and MultiProposal Operator

* add unittest skip for test_multi_proposal_op

* retrigger test

* optimize multi proposal operator (cpu implementation)

* open the cpu/gpu consistency test for Proposal Op and MultiProposal Op

CONTRIBUTORS.md

@@ -160,3 +160,4 @@ List of Contributors
 * [Sorokin Evgeniy](https://github.com/TheTweak)
 * [dwSun](https://github.com/dwSun/)
 * [David Braude](https://github.com/dabraude/)
+* [Kan Wu](https://github.com/wkcn)