digiKam port to QtAV/ffmpeg instead Qt5Multimedia : port Presentation audio player to QtAV.

TODO:

- handle video rotation flag with new Exiv2 0.26 to autorotate media in player.
- port video thumbnailer to QtAV.
- remove Qt5Multimedia dependency.

For later:

- play video into slideshow tool.
- port old videoslideshow tool to QtAv.

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