* dnn/Vulkan: fix GPU hang for heavy convolution tasks

Intel i915 driver will declare GPU hang if the compute shader
takes too long to complete. See
https://bugs.freedesktop.org/show_bug.cgi?id=108947 for details.

The idea in this commit is to divide heavy task into several light
ones and run compute shader multiple times to make each run take
short time enough.

TODO: Add more efficient compute shader
Signed-off-by: Wu Zhiwen <zhiwen.wu@intel.com>

* dnn/Vulkan: add a more efficient conv shader

* Split videoio dependencies search into pieces, removed obsolete backends

Stitching: multi-feed on gain and block compensator (#13503)

* multi-feed on gain and block compensator

* ABI compatibility

OpenCV 4.0.1

OpenCV 4.0.1 for Intel(R) OpenVINO(TM) toolkit

Commit: 124011c3
PR: https://github.com/opencv/opencv/pull/13392

Sobel filter with 16S/16U datatype is broken.

OpenCV 3.4.5

backport 4ba4901c

https://software.intel.com/en-us/openvino-toolkit

* Fix python bindings without stitching module

* stitching: move stitching specific code into modules/stitching/misc