Fading out on song change was not working, if UpMixing is selected
Mantis #4322 : Handle first failed generation thumbnail, it fix Music Thumbnail.
Added some missing pngs:
- previewbackground.png (see Mantis 4379)
- defaultRemovable.png
- defaultRemovableBIG.png
for both Default skins
Restore TvLibrary.sln AnyCPU wrong commit.
On some occasions the Upmixing flag was not honored and fadeoutr did not work
Mantis #4060 corrected TvLibrary.sln / Merge branch 'BUG-Restore_AnyCPU_Solution'
Merge branch 'master' of https://github.com/MediaPortal/MediaPortal-1 into BUG-4375-Music_FadeOut_on_song_change_not_working_with_Upmixing
Merge branch 'BUG-4375-Music_FadeOut_on_song_change_not_working_with_Upmixing'
Mantis #3935 : WIP Audio Channel Count for Internal Blu-ray.
Merge remote-tracking branch 'remotes/origin/FEAT-3935-Add_audio_channel_count_information_for_the_Blu-ray_audio_streams'
Merge branch 'master' of https://github.com/MediaPortal/MediaPortal-1

Conflicts:
	mediaportal/Core/Util/Picture.cs