Soomin Lee authored Oct 30, 2019 and Jean-Baptiste Kempf committed Oct 31, 2019

Move supported playlists files to the medialibrary discoverable path
at the end of a 4sec timer.

Indeed, in the case where the playlist was downloaded first, it could
lead to having ghost playlists since the medialibrary parsed the
playlist with yet nonexistent media files.

Closes #759