Hot fix negative MTCNN PNet ROI coordinates

* fix negative roi start

* some more experiments

* clean up

Remove custom transpose kernel from MTCNN sample

G-API: Python. Wrapper for networks.

* Python networks

* Added pyopencv_to

* Changed work with pyopencv_to

Add streaming queue capacity option choice to MTCNN G-API sample

* Add streaming queue capacity option

* trying to fix mac build

* rename face detection sample

G-API MTCNN demo hotfix to align overall pipeline accuracy with the reference Python code output.

* MTCNN G-API demo aligned with Python from OMZ

* clean up

* more comments from Maxim are addressed.

* address comment from Dmitry

G-API MTCNN sample

* add face detection demo

* clean up

* enable back accumulate

* additional input

* meta args workaround

* additional arg

* add init

* roll back

* fix shadowing

* roll back

* clean up and PNet copy from debug branch which now works

* try nets operator

* more clean up

* more clean up

* add 6 layers pyramid experimental code

* final clean up and ready for PR

* original image resize

* Remove Pnet declarations. Generic infer is used now.

* scales and sizes calculation added

* fix assert, and add ceil to size calculation

* try doubles for scales

* Address comments from Dmitry.

* use half scale option

* fix half scale

* clean up debug outputs

* try to get input image width and height

* clean up

* trailing spaces and review from Maxim

* more comments from Maxim are addressed

* try to fix warnings

* try to fix warnings and address more comments from Dmitry

* crop fix and clean up

* more warnings fixes

* more warnings fixes

* more comments from Maxim are addressed

* even more consts

* copy_n for regressions

* address more comments from Dmitry

* more comments from Maxim