(cherry picked from commit e650d87e)
(cherry picked from commit ca9c52ac)

Conflicts:
	cmake/OpenCVPackaging.cmake

Everything else depends on it, after all.

(cherry picked from commit cf54e3b9)

Conflicts:
	cmake/OpenCVPackaging.cmake

(cherry picked from commit 6d52ea89)

Which also happens to align the non-Debian specific variables
with the ones used by upstream CMake.

(cherry picked from commit b8c60234)

Conflicts:
	cmake/OpenCVPackaging.cmake

They don't actually do anything. And even if they did, all components are
enabled by default, anyway.

(cherry picked from commit 49fe4969)

Conflicts:
	cmake/OpenCVPackaging.cmake

Added opencv_testing.sh.in file;
opencv_testing.sh installation guarded by OS check.

Env setup for testing package implemented using /etc/profile.d;
Variable with path for all native samples added;
Path for test binaries and test data updated.