* Started to write nGraph reference implementation of the operation ExperimentalDetectronTopKROIs.
* Written cpp-file for the nGraph reference implementation of the operation ExperimentalDetectronTopKROIs.
* Code style fixes.
* Started to write evaluate() (in evaluates_map.cpp) for the nGraph operation ExperimentalDetectronsTopKROIs.
* Code style fixes.
* Written evaluate() for ExperimentalDetectronTopKROIs.
* Small fixes.
* Written test for ExperimentalDetectronTopKROIs evaluation.
* Small fix.
* Fixed Apache license header.
* Some changes.
* int64_t was replaced with size_t in the body of ngraph::runtime::reference::experimental_detectron_topk_rois().
* Added more test for evaluation of ExperimentalDetectronTopKROIs.