gpu implementation of Dual TV-L1 Optical Flow
fixed static build of gpu module with ffmpeg:

multiple definition of cap_ffmpeg_impl.hpp functions in gpu and highgui
fix warning in CUDA samples
GPU interface for soft cascade
soft cascade: gpu representation
precompute feature response for scaling factor
GPU soft cascade: buffers preallocation
integral channel storage are cached as a cascade's field
CUDA callers
fix typo in cascade loading
add performance test for GPU soft cascade
CUDA kernels interface
fix compilation
fix data paths in performance test
add shrinking kernel
add detections vector initialization in tests
first version of soft cascade on GPU
remove dead code
fix cast bug; add logging
refactor logs