* Android build improvements
* look for NDK in "ndk-bundle" directory under the SDK directory if location not specified
* look for cmake and ninja in "cmake" directory under the SDK directory if not found in the path
* disable use of ccache if not found in the path
* Redo build tool existence checks
- configuration files for ABIs configuration
- use builtin Android NDK's toolchain by default (force flag to use OpenCV's toolchain)
- default values for 'work_dir' and 'opencv_dir'
- fix Javadoc:
- generate Javadoc after gather step to process all Java files (including Android 21)
- generate into 'OpenCV-android-sdk' directly without additional copy step
- use smart copy/move utility functions ('shutil' doesn't well with existed destination)
- by default move files to reduce pressure on storage I/O (> 800Mb)
- IPP is disabled by default when compiler is mingw (couldn't make it
work)
- fixed some warnings
- fixed some `__GNUC__` version checks (for correctness and convenience)
- removed UTF-8 BOM from hough.cpp (fixes#5253)