Documentation generation refactoring (#10621)

* Documentation build updates:

- disable documentation by default, do not add to ALL target
- combine Doxygen and Javadoc
- optimize Doxygen html

* javadoc: fix path in build directory

* cmake: fix "Documentation" status line

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

 [~] Automatically tracked dependencies between modules
 [+] Support for optional module dependencies
 [+] Options to choose modules to build
 [~] Removed hardcoded modules lists from OpenCVConfig.cmake, opencv.pc and OpenCV.mk
 [+] Added COMPONENTS support for FIND_PACKAGE(OpenCV)
 [~] haartraining and traincascade are moved outside of modules folder since they aren't the modules

modified highgui and ts modules and cmakelists for ios cross-compiling, added ios toolchains, added ios build tutorial

Turned off android camera and java wrappers for low Android API levels (android-8 is required for these components)

Fixed tests compilation issue with low Android API levels. OpenCV successfully compiles for API level 3 and above.
Enable tests for Android by default.

reworked nearly all of the OpenCV tests (except for opencv_gpu tests) - they now use the Google Test engine.

mainly cmake stuff, but in persistance the wcstombs
is not supported on android, and in
sift.cpp there was and ifdef that affected arm and this
causes undefined symbols on android.

some refactoring
added gpu module to compilation

Simple implementation of StereoBM_GPU.
It is excluded from compilation now.