- Optimizations set change. Now IPP integrations will provide code for SSE42, AVX2 and AVX512 (SKX) CPUs only. For HW below SSE42 IPP code is disabled.
- Performance regressions fixes for IPP code paths;
- cv::boxFilter integration improvement;
- cv::filter2D integration improvement;

- removed OpenCV_LIB_DIR* vars (they are broken and not required anymore)
- OpenCVConfig.cmake doesn't contain ANDROID/CUDA code if there is no such support
- removed OpenCV2_INCLUDE_DIRS_CONFIGCMAKE, merged into OpenCV_INCLUDE_DIRS_CONFIGCMAKE
- fix hard-coded relative paths for OpenCV_INSTALL_PATH
- removed OpenCV_TBB_ARCH
- switch OpenCVConfig.cmake into 2-level mode for Android SDK

explained reason why IPP is disabled on 32-bit Linux. disable IPP's minMaxLoc_32f on 32-bit OSes only

2) disable IPP on 32-bit Linux when OpenCV is built as shared libs. Otherwise we get linker errors
3) disable IPP's minMaxIdx 32-bit floating-point flavor in a hope that it fixes some test failures

disabled 64f IPP DFT; added IPP Gaussian filter; added IPP GetRectSubPix; added IPP BilateralFilter (temporarily disabled)

Started top-level CMakeLists.txt file reorganization: cmake scripts are moved to separate folder; refactored BUILD_*, INSTALL_*, ENABLE_*, USE_*, WITH_* options.