GAPI: Migration to IE Core API
* Migration to IE Core API
- both versions are maintained
- checked building with all the OpenVINO versions (2019.R1, R2, R3, 2020.4 (newest))
* commit to awake builders
* Addressing comments
- migrated to Core API in 'gapi_ie_infer_test.cpp'
- made Core a singleton object
- dropped redundant steps
* Addressing comments
- modified Mutex locking
* Update
* Addressing comments
- remove getInitMutex()
- reduce amount of #ifdef by abstracting into functions
* return to single IE::Core
* Divide functions readNet and loadNet to avoid warnings on GCC
* Fix deprecated code warnings
* Fix deprecated code warnings on CMake level
* Functions wrapped
- All the functions depended on IE version wrapped into a cv::gapi::ie::wrap namesapace
- All this contained to a new "giebackend/gieapi.hpp" header
- The header shared with G-API infer tests to avoid code duplications
* Addressing comments
- Renamed `gieapi.hpp` -> `giewrapper.hpp`, `cv::gapi::ie::wrap` -> `cv::gimpl::ie::wrap`
- Created new `giewrapper.cpp` source file to avoid potential "multiple definition" problems
- removed unnecessary step SetLayout() in tests
* Enabling two NN infer teest
* Two-NN infer test change for CI
- deleted additional network
- inference of two identical NN used instead
* Fix CI fileNotFound
* Disable MYRIAD test not to fail Custom CI runs
Introducing the sample of Face Beautification algorithm implemented via Graph-API
* Introducing the sample of Face Beautification algorithm implemented via Graph-API
- 'gapi/samples/face_beautification.cpp' added
- FIXME added in 'gcpukernel.hpp'
* INF_ENGINE fix
- preprocessing clauses added not to run the sample without Inference Engine
* INF_ENGINE fix 2
- warnings removed
* Fixes
- checking IE version cut as there is no dependency
- some alignments fixed
- the comment about preprocessing commands fixed
* ie::backend() issue fix (according to dmatveev)
- as the sample needs the cv::gapi::ie::backend() to be defined regardless of having IE or not, there is its throw-error definition in `giebackend.cpp` now (by dmatveev)
- for the same reason, #includes in `giebackend.hpp` are fixed
- HAVE_INF_ENGINE check is removed from the sample
* G-API-NG/API: Introduced inference API and IE-based backend
- Very quick-n-dirty implementation
- OpenCV's own DNN module is not used
- No tests so far
* G-API-NG/IE: Refined IE backend, added more tests
* G-API-NG/IE: Fixed various CI warnings & build issues + tests
- Added tests on multi-dimensional own::Mat
- Added tests on GMatDesc with dimensions
- Documentation on infer.hpp
- Fixed more warnings + added a ROI list test
- Fix descr_of clash for vector<Mat> & standalone mode
- Fix build issue with gcc-4.8x
- Addressed review comments
* G-API-NG/IE: Addressed review comments
- Pass `false` to findDataFile()
- Add deprecation warning suppression macros for IE
