* OpenVX HAL updated to use generic OpenVX wrappers

* vxErr class from OpenVX HAL replaced with ivx::WrapperError

* reduced usage of vxImage class from OpenVX HAL replaced with ivx::Image

* vxImage class rewritten as ivx::Image subclass that calls swapHandle prior release

* Fix OpenVX HAL build

* Fix for review comments

(2.4) Backports from master branch (#7854)

Several fixes for OpenVX wrappers (#7782)

* Several fixes added to ivx.hpp:
* `#include <VX/vxu.h>`
* `vx_keypoint_t` support added
* type check fixed
* fixed Node::create() for >6 args in c++98
* fixed Array::copyFrom() if array is empty
* type check changed; Array::addItem methods changed

Versions:
- ffmpeg 3.2.1 (was 3.1.3)
- openh264 1.6.0 (was 1.5.0)
- libvpx 1.6.0 (was 1.5.0)

* fixing 1.0.1

* fixing build without c++11

* hiding warnings

* fixing 1.0.1
* fixing build without c++11

OpenVX C++ wrappers docs (#7681)

* adding wrapper headers to the project to see them in IDE project explorer

* readme

* doxygen: toplevel brief-s

* more doxygen

* more doxygen