Signed-off-by: Li Peng <peng.li@intel.com>

Found via `codespell`

The ocl convolution doesn't support tensorflow padMode well.
Add fallback check if we meet this situation, it could fix the
tensorflow MobileNet SSD failure.
Signed-off-by: Li Peng <peng.li@intel.com>

Signed-off-by: Li Peng <peng.li@intel.com>

Added group targets for samples (opencv_samples, opencv_samples_<group>), install samples/data inseparate component 'samples_data'

- allow installing samples sources on all platforms
  even if BUILD_EXAMPLES is disabled,  fixed minor
  issues in sources installation process
- use 'example_<group>_<name>' scheme for target and binary file naming
- use single function for sample executable creation

- use per-module includes instead of "opencv.hpp"
- unused function warnings
- undefined macro warning