* matlab: move to opencv_contrib

* cmake: preserve variables scope for processing modules

- use macro instead of function to avoid scope resets

* Add HPX backend for OpenCV implementation
Adds hpx backend for cv::parallel_for_() calls respecting the nstripes chunking parameter. C++ code for the backend is added to modules/core/parallel.cpp. Also, the necessary changes to cmake files are introduced.
Backend can operate in 2 versions (selectable by cmake build option WITH_HPX_STARTSTOP): hpx (runtime always on) and hpx_startstop (start and stop the backend for each cv::parallel_for_() call)

* WIP: Conditionally include hpx_main.hpp to tests in core module
Header hpx_main.hpp is included to both core/perf/perf_main.cpp and core/test/test_main.cpp.
The changes to cmake files for linking hpx library to above mentioned test executalbles are proposed but have issues.

* Add coditional iclusion of hpx_main.hpp to cpp cpu modules

* Remove start/stop version of hpx backend

- tests for both SIMD128 / SIMD256
- different dispatched + baseline(SIMD128) intrinsics

during opencv_world builds

to reduce overhead of gradle builds

Added group targets for samples (opencv_samples, opencv_samples_<group>), install samples/data inseparate component 'samples_data'

- allow installing samples sources on all platforms
  even if BUILD_EXAMPLES is disabled,  fixed minor
  issues in sources installation process
- use 'example_<group>_<name>' scheme for target and binary file naming
- use single function for sample executable creation

Found via `codespell -i 3 -w --skip="./3rdparty" -I ../opencv-whitelist.txt`

* Do not build protobuf if dnn is disabled

* Added BUILD_LIST cmake option to the cache

* Moved protobuf to the top level

* Fixed static build

* Fixed world build

* fixup! Fixed world build

fixes CUDA build

To reduce number of unnecessary rebuilds on updates of OpenCL kernels

- use suffixes like '.avx.cpp'
- added CMake-generated files for '.simd.hpp' optimization approach
- wrap HAL intrinsic headers into separate namespaces for different build flags
- automatic vzeroupper insertion (via CV_INSTRUMENT_REGION macro)