* Draft version of new approach for Proposal sub-graph conversion for TF OD API models
* Added clip_after_nms = True for Proposal sub-graph being replaced with DetectionOutput
* Refactored code to insert DetectionOutput instead of Proposal operation
* Code cleanup
* Added separate function to insert DetectionOutput instead of Proposal operation
* Updated transformation configuration files for the TF OD API models with Proposal transformation
* Code refactoring
* Code refactoring
* Fix for the condition
* Fixed transformation
* Fixed transformation. One more time
* Updated document about conversion of the TF OD API models
* Update code comments