(cherry picked from commit bba8c0be)

(cherry picked from commit ff002203)

fixed trailing whitespaces
renamed files *vaapi* to *va_intel*
changed names vaapi* to va_intel*

fixed whitespaces
fixed issues
fixed issue
fixed module statement issues
fixed access mode
added initialization check
fixed warning

057cd52 first versions: cv::ogl::convertFromGLTexture2D & cv::ogl::convertToGLTexture2D
5656e94 added autogenerated stuff for cl_gl.h
765f1fd resolved CL functions in opengl.cpp
9f9fee3 implemented function cv::ogl::ocl::initializeContextFromGLTexture2D()
a792adb cv::ogl::ocl::initializeContextFromGLTexture2D() - added linux support (glx.h)
51c2869 added missing error message in function cv::ogl::ocl::initializeContextFromGLTexture2D()
513b887 fixed extension call in function cv::ogl::ocl::initializeContextFromGLTexture2D()
475a3e9 added CL-GL interop Windows sample (gpu/opengl_interop.cpp)
07af28f added building of CL-GL interop sample - Windows only
befe3a2 fixed whitespace errors & doxygen warnings (precommit_docs)
551251a changed function name to cv::ogl::ocl::initializeContextFromGL(), removed unused argument
4d5f009 changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR
9fc3055 changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KH
6d31cee Revert "changed CL_DEVICES_FOR_GL_CONTEXT_KHR to CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KH"
cc6a025 added texture format check in cv::ogl::convertFromGLTexture2D()
063a2c1 CL-GL sample: added Linux implementation (Xlib/GLX)
c392ae9 fixed trailing whitespace
85a80d0 fixed include files
ae23628 excluded samples/opengl from build case 2
9870ea5 added android EGL support
530b64c added doxygen documentation comments to CL-GL interop functions

Commits:
added new function, cv::ocl::attachContext(String& platformName, void* platformID, void* context, void* deviceID) which allow to attach externally created OpenCL context to OpenCV.
add definitions of clRetainDevice, clRetainContext funcs
removed definitions for clRetainContext, clRetainDevice
fixed build issue under Linux
fixed uninitialized vars, replace dbgassert in error handling
remove function which is not ready yet
add new function, cv::ocl::convertFromBuffer(int rows, int cols, int type, void* cl_mem_obj, UMat& dst, UMatUsageFlags usageFlags = cv::USAGE_DEFAULT) which attaches user allocated OpenCL clBuffer to UMat
uncommented clGetMemObjectInfo definition (otherwise prevent opencv build)
fixed build issue on linux and android
add step parameter to cv::ocl::convertFromBuffer func
suppress compile-time warning
added sample opencl-opencv interoperability (showcase for cv::ocl::convertFromBuffer func)
CMakeLists.txt modified to not create sample build script if OpenCL SDK not found in system
fixed build issue (apple opencl include dir and spaces in CMake file)
added call to clRetainContext for attachContext func and call to clRetainMemObject for convertFromBuffer func
uncommented clRetainMemObject definition
added comments and cleanup
add local path to cmake modules search dirs (instead of replacing)
remove REQUIRED for find_package call (sample build together with opencv). need to try standalone sample build
opencl-interop sample moved to standalone build
set minimum version requirement for sample's cmake to 3.1
put cmake_minimum_required under condition, so do not check if samples not builded
remove code dups for setSize, updateContinuityFlag, and finalizeHdr
commented out cmake_minimum_required(VERSION 3.1)
add safety check for cmake version
add convertFromImage func and update opencl-interop sample
uncommented clGetImageInfo defs
uncommented clEnqueueCopyImageToBuffer defs
fixed clEnqueueCopyImageToBuffer defs
add doxygen comments
remove doxygen @fn tag
try to restart buildbot
add doxygen comments to directx interop funcs
remove internal header, use fwd declarations in affected compile units instead

Conflicts:
	samples/CMakeLists.txt

removed contrib, legacy and softcsscade modules; removed latentsvm and datamatrix detector from objdetect. removed haartraining and sft apps.
some of the stuff will be moved to opencv_contrib module.
in order to make this PR pass buildbot, please, comment off opencv_legacy, opencv_contrib and opencv_softcascade test runs.

Allow to build samples via OpenCV binaries from distribution package
(find_package with OpenCV_DIR).

 [~] 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

2) NVidia tests for GPU
3) FD sample that uses NVidia's interface.