1) Document GFrame/MediaFrame (and also other G-API types)
- Added doxygen comments for GMat, GScalar, GArray<T>, GOpaque classes;
- Documented GFrame and its host-side counterpart MediaFrame;
- Added some more notes to the data type classes.
2) Give @brief descriptions to most of the cv::gapi::* namespaces
3) Make some symbols private
- These structures are mainly internal and shouldn't be used directly
* G-API: Addressed various documentation issues
- Fixed various typos and missing references;
- Added brief documentaion on G_TYPED_KERNEL and G_COMPOUND_KERNEL macros;
- Briefly described GComputationT<>;
- Briefly described G-API data objects (in a group section).
* G-API: Some clean-ups in doxygen, also a chapter on Render API
* G-API: Expose more graph compilation arguments in the documentation
* G-API: Address documentation review comments
G-API: Kernel package design (#13851)
* Remove cv::unite_policy from API
* Add check that all id in kernel package are unique
* Refactor checker id procedure
* Remove cv::gapi::GLookupOrder from API
* Implement cv::gapi::use_only
* Fix samples
* Fix docs
* Fix comments to review
* Remove unite_policy
* Fix GKernelPackage::backends()
* Fix comments to review
* Fix all_unique
* Fix comments to review
* Fix comments to review
* Remove out of date tests
G-API: Doxygen class reference
* G-API Doxygen documentation: covered cv::GComputation
* G-API Doxygen documentation: added sections on compile arguments
* G-API Doxygen documentation: restructuring & more text
* Added new sections (organized API reference into it);
* Documented GCompiled, compile args, backends, etc.
* G-API Doxygen documentation: documented GKernelPackage and added group for meta
